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RESEARCHOpenAccessComparativecostassessmentoftheKato-KatzandFLOTACtechniquesforsoil-transmittedhelminthdiagnosisinepidemiologicalsurveysBenjaminSpeich1,2,StefanieKnopp1,2,KhalfanAMohammed3,ISimbaKhamis3,LauraRinaldi4,GiuseppeCringoli4,DavidRollinson5,JürgUtzinger1,2*AbstractBackground:TheKato-Katztechniqueiswidelyusedforthediagnosisofsoil-transmittedhelminthiasisinepidemiologicalsurveysandisbelievedtobeaninexpensivemethod.
TheFLOTACtechniqueshowsahighersensitivityforthediagnosisoflight-intensitysoil-transmittedhelminthinfectionsbutisreportedtobemorecomplexandexpensive.
Weassessedthecostsrelatedtothecollection,processingandmicroscopicexaminationofstoolsamplesusingtheKato-KatzandFLOTACtechniquesinanepidemiologicalsurveycarriedoutinZanzibar,Tanzania.
Methods:Wemeasuredthetimeforthecollectionofasinglestoolspecimeninthefield,transfertoalaboratory,preparationandmicroscopicexaminationusingstandardprotocolsfortheKato-KatzandFLOTACtechniques.
Salariesofhealthworkers,lifeexpectancyandassetcostsofmaterials,andinfrastructurecostsweredetermined.
TheaveragecostforasingleorduplicateKato-KatzthicksmearsandtheFLOTACdualordoubletechniquewerecalculated.
Results:TheaveragetimeneededtocollectastoolspecimenandperformasingleorduplicateKato-KatzthicksmearsortheFLOTACdualordoubletechniquewas20minand34sec(20:34min),27:21min,28:14minand36:44min,respectively.
ThetotalcostsforasingleandduplicateKato-KatzthicksmearswereUS$1.
73andUS$2.
06,respectively,andfortheFLOTACdoubleanddualtechniqueUS$2.
35andUS$2.
83,respectively.
Salariesimpactedmostonthetotalcostsofeithermethod.
Conclusions:Thetimeandcostforsoil-transmittedhelminthdiagnosisusingeithertheKato-KatzorFLOTACmethodinepidemiologicalsurveysareconsiderable.
Ourresultscanhelptoguidehealthcaredecisionmakersandscientistsinbudgetplanningandfundingforepidemiologicalsurveys,anthelminthicdrugefficacytrialsandmonitoringofcontrolinterventions.
BackgroundChronicinfectionswithoneorseveralofthecommonsoil-transmittedhelminths,Ascarislumbricoides,Tri-churistrichiuraandthehookworms(Ancylostomaduo-denaleandNecatoramericanus),mightaccountforaglobalburdenof39milliondisability-adjustedlifeyears(DALYs)lostannually[1,2].
School-agedchildreninthedevelopingworldareathighestriskofmorbidityduetosoil-transmittedhelminthiasis.
Inthecurrenteraof'preventivechemotherapy',thatisthelarge-scaleadministrationofanthelminthicdrugstoschool-agedchildrenandotherpopulationsatriskofmorbidity[3],diagnosisisoftenneglectedandcost-effectivenessconsiderationsarenecessary.
Yet,diagnosisisofparamountimportanceforanaccurateassessmentoftheepidemiologicalsituationandburdenofdiseaseestimations,andformonitoringdrugefficacyandphar-macovigilance[4-7].
Inepidemiologicalsurveyspertain-ingtosoil-transmittedhelminthiasis(andintestinal*Correspondence:juerg.
utzinger@unibas.
ch1DepartmentofEpidemiologyandPublicHealth,SwissTropicalandPublicHealthInstitute,Basel,SwitzerlandFulllistofauthorinformationisavailableattheendofthearticleSpeichetal.
Parasites&Vectors2010,3:71http://www.
parasitesandvectors.
com/content/3/1/712010Speichetal;licenseeBioMedCentralLtd.
ThisisanOpenAccessarticledistributedunderthetermsoftheCreativeCommonsAttributionLicense(http://creativecommons.
org/licenses/by/2.
0),whichpermitsunrestricteduse,distribution,andreproductioninanymedium,providedtheoriginalworkisproperlycited.
schistosomiasis),theKato-Katztechnique[8]isawidelyuseddiagnosticapproach[2,9-11].
Indeed,themethodisrelativelystraightforward,requiresminimalequipmentwhichismostlyreusable,andhencethemethodisthoughttobeinexpensive[7,10].
Moreover,theKato-Katzmethodissimpletoapplyandlaboratoryworkerscanbetrainedwithinhalfaday[12].
AdrawbackoftheKato-Katzmethod,however,isitslackofsensitivityfordetectinglight-intensitysoil-transmittedhelminthinfec-tions[9,13].
NewresearchhasrevealedthattherecentlydevelopedFLOTACtechnique[14]showsahighersen-sitivitythanmultipleKato-Katzthicksmearsforthediagnosisofsoil-transmittedhelminthinfections[15-17].
ComparedtotheKato-Katzmethod,theFLOTACisamorecomplicatedtechnique,andhencerequiresbetterequippedlaboratories[18-20]andmoreextensivetrain-ingoflaboratoryworkers.
Here,aneconomicevaluationoftheKato-KatzandFLOTACtechniqueswasperformedwithintheframeofanepidemiologicalsurvey.
Specifically,thecostsrelatedtostoolcollection,transfertothelaboratory,prepara-tionandmicroscopicexaminationofsingleanddupli-cateKato-KatzthicksmearsandtheFLOTACdualordoubletechniqueweredetermined.
Thisinformationisrelevantforresearchersanddiseasecontrolmanagersfortheplanningofepidemiologicalsurveysandthemonitoringandevaluationofsoil-transmittedhel-minthiasiscontrolprogrammes.
MaterialsandmethodsStudyarea,populationandethicalconsiderationsThisstudywascarriedoutonUnguja,thelargestislandbelongingtotheZanzibararchipelagoinTanzania,betweenMarchandMay2009.
ThetwoprimaryschoolsofKinyasiniandKilombero,located26and32kmnorth-eastofZanzibarTown,weretheselectedfieldsites.
LaboratoryexaminationswereconductedintheHelminthControlLaboratoryUnguja(HCLU),inZanzi-barTown.
Thestudywasreadilyembeddedinarando-misedcontrolledtrial,assessingtheefficacyandsafetyoffouranthelminthicdrugregimensagainstT.
trichiuraandothersoil-transmittedhelminths.
Atthebeginningofthestudy,1,066schoolchildrenagedbetween6and20years,werescreenedforsoil-transmittedhelminthinfections(KnoppS,MohammedKA,SpeichB,Hatten-dorfJ,KhamisIS,KhamisAN,StothardJR,RollinsonD,MartiH,UtzingerJ:"AlbendazoleandmebendazoleadministeredaloneorincombinationwithivermectinagainstTrichuristrichiura:arandomizedcontrolledtrial",submitted).
ThestudywasapprovedbytheethicscommitteeofBasel,Switzerland(EKBB;referenceno.
13/09)andtheMinistryofHealthandSocialWelfare(MoHSW)ofZanzibar(referenceno.
ZAMEC/0001/09).
Parentsorlegalguardiansofparticipatingchildrensignedawritteninformedconsentsheet.
Childrenconsentedorallytoparticipate.
Attheendofthestudy,allchildrenattend-ingtheprimaryschoolsofKinyasiniandKilomberoweretreatedwithsingleoraldosesofalbendazole(400mg)andpraziquantel(40mg/kg)freeofcharge.
FieldandlaboratoryproceduresTheheadmastersofKinyasiniandKilomberoprimaryschoolswereinformedaboutthepurposeandproce-duresofthestudy.
Afterhavingobtainedwritteninformedconsentbytheparents/legalguardiansandoralconsentbythechildren,thefieldworkwaslaunched.
Everymorning,startingat07:00hoursatHCLU,stoolcontainersandcollectionshelveswereloadedontoa4-wheeldrive(4-WD)car,andateamconsistingof4-6workersfromHCLUvisitedeitherKinyasiniorKilomberoschools.
Theteamlabeledemptycontainerswithuniqueidentification(ID)num-bers,distributedthesetothechildrenandcollectedfilledcontainersthathadbeendistributedthedaybefore.
Eachday,approximately100childrenwereenrolledandlime-sizedearlymorningstoolsampleswerecollected.
ThefilledcontainersweretransferredtoHCLUwithin2-3handprocessedasfollows.
ImmediatelyafterarrivalatHCLU,duplicateKato-Katzthicksmearsfromeachstoolsamplewerepreparedby2-8membersofHCLU,using41.
7mgtemplates[8].
Afteraclearingtimeof20-40min,eachKato-Katzthicksmearwasexaminedquan-titativelyforhookwormeggsbyoneoffourexperiencedmicroscopists.
Intheafternoon,3-6hafterslideprepara-tion,thethicksmearswerere-examinedbyoneoffouradditionalmicroscopists,whocountedeggsofA.
lumbri-coidesandT.
trichiuraandrecordedthemseparately.
OnceaKato-Katzthicksmearhadbeenprepared,thestoolsamplewasplacedbackintothecollectionshelforderedbyincreasingID.
Athirdofthestoolsampleswastakenandasmallamountofstoolwasweighedto~1gusingaKernbalance(EMBbasicbalance;Ballin-gen-Frommern,Germany)andpreservedinapre-labeledtubecontaining10mlof5%formaldehyde.
Thepreservedstoolsampleswerestoredatroomtempera-tureandexaminedbytheFLOTACtechniquewithin3weeksaftercompletionoftheclinicaltrialinlateMay2009[14].
WhiletechniciansfromHCLUwerealreadyacquaintedwiththeKato-Katztechnique,a3-daytrain-ingcoursewasofferedfortheFLOTACtechnique,facilitatedbytwoexpertsfromtheUniversityofNaples,Italy.
Duringthetraining,theFLOTACdualtechniquewasemployed,usingflotationsolutions4(FS4;sodiumnitrate,NaNO3,specificgravity(s.
g.
)=1.
20)and7(FS7;zincsulfate,ZnSO4·7H2O,s.
g.
=1.
35).
Speichetal.
Parasites&Vectors2010,3:71http://www.
parasitesandvectors.
com/content/3/1/71Page2of11TheindividualstepsforFLOTACpreparationandmicroscopicexaminationofstoolsampleswereper-formedby8-12membersofHCLUandaredetailedinTable1.
PreliminaryresultsshowedthatFS4outper-formedFS7forthediagnosisofsoil-transmittedhel-minths,andhenceFS4wasusedthroughout.
IndividualstoolsampleswerepreparedaccordingtotheFLOTACdualtechnique[14].
Inbrief,~1gofstoolwasequallydistributedtothetwochambersoftheFLOTACappa-ratus,butinsteadofusingtwodifferentflotationsolu-tions,FS4wasappliedinbothchambers.
Hence,thereadingofthechamberswasperformedaccordingtotheFLOTACbasictechnique[14].
CostestimationsToassessthecostsforsingleandduplicateKato-KatzthicksmearsandtheFLOTACdualordoubletechni-que,thefollowingexpensesweredetermined:(i)costsduetosalaries;(ii)costsduetomaterials;and(iii)costsduetoinfrastructure.
Wemadethefollowingassump-tions:screeningof3,000childrenforsoil-transmittedhelminthinfectionsbyanexperiencedresearchteam,Table1WorkingstepsandnumberoftimemeasurementstodeterminethecostsoftheKato-KatzandFLOTACmethodforthediagnosisofsoil-transmittedhelminthsinZanzibarWorkingstepnNumberofmeasurementsaKato-Katz(K-K)measurements(K1a)LabelingofK-Kslides10919*5;2*4;1*6(K1b)PreparationofduplicateK-Kslides137121*1;6*0.
5;5*2;1*3(K2)Microscopymorning34132*1;22*2;22*8;21*4;1*5(K3)Microscopyafternoon39644*1;26*8;24*2;24*4(K6a)WashingofK-Kslides1801*180(K6b)Washingspatulaandtemplate2971*91;1*96;1*110(K6c)Cuttingcellophanepaper821*82(K6d)Cuttingwiremesh2061*206FLOTACmeasurements(F1)Measurementof1gofstoolandhomogenization16829*5;1*6;1*7;1*10(F2a)Filter(inclusivelabeling)3131*1(F2b)Filter(exclusivelabeling)4125*1;4*3;2*2(F2c)LabelingFalcontubes333*6;2*4;1*7(F3)CentrifugationoftubesandfillingwithFS6220*3;1*2(F4)AssemblingFLOTACapparatus2929*1(F5)FillingFLOTACapparatus5555*1(F6)CentrifugationandtranslationofFLOTACapparatus3618*2(F7)Readingfirstchamber120120*1(F8)Readingsecondchamber119119*1(F11a)Washingfilterandbeaker829*1;9*6;1*4;1*7;1*8(F11b)OpeningFLOTACapparatus5233*1;1*2;1*3;1*14(F11c)WashingFLOTACapparatus262*3;1*2;1*4;1*14(F11d)WashingFalcontube2083*4;2*5;1*101;1*84;1*1(F11e)Washingpipettes2009*1;1*105;1*84;1*1Measurementsforbothtechniques(S1-S3)Collectionofstoolsamplesatschool2,921b(K4/F9)Dataentry(demographicdata)131*13(K5/F10)Dataentry(results)4075*22;5*23;3*20;3*9;2*14;1*5;1*15;1*21;1*26(K6f/F11f)Puttingapieceofpaperintoanemptycontainertoalleviatecleaningofcontainer1387*10;1*68(K6g/F11g)Removingstooloutofcontainer(beforecleaning)2604*10;2*36;1*38;1*52;1*58(K6h/F11h)Washingofstoolcontainer(withoutlid)655*10;1*15(K6i/F11i)Washinglid563*10;1*5;1*6;1*15(K6j/F11j)ErasingofIDsfromstoolcontainer29018*10;1*110aInterpretedasfollows:forexample,intheworkingstep"LabelingofK-Kslides"itwasmeasured19timeshowmuchtimewasrequiredtolabel5slides,2timesthetimeforlabeling4slidesandoncethetimeforlabeling6slides.
b2,921stoolsampleswerecollectedin38visitsatschools,wherealwaysadifferentnumberofstoolsampleswascollected.
Speichetal.
Parasites&Vectors2010,3:71http://www.
parasitesandvectors.
com/content/3/1/71Page3of11with100stoolsamplesexaminedperdayinalaboratory(Appendix).
TheflowofcostdeterminationisshowninFigure1.
Allcostsarereportedin2009US$.
CostsduetosalariesToassessthecostsduetosalaries,thesalaryofeachmemberoftheHCLU,accordingtohisorherprofes-sionaldegree,wasdeterminedusingaquestionnaire.
Additionally,thetimeforeachworkingstepinthefieldandinthelaboratorywasmeasuredseveraltimesandaveraged.
Finally,thenumberofemployeeswithaspeci-ficoccupationneededtocollect,processandexamine100stoolsamplesperdayusingtheKato-KatzorFLO-TACtechniquewascalculated.
Forthecollectionofstoolsamplesinthefieldthefol-lowingstepswererecorded:(i)thetimefromdepartureinthelaboratory,schoolvisitandreturntothelabora-tory;(ii)thenumberofpersonnelwhovisitedtheschool;and(iii)thenumberofstoolsamplescollectedperday.
Usingthesedata,theaverageperson-timetocollectonestoolsamplewasestimated.
ThedurationofeachdistinctstepinthelaboratoryneededtoperformtheKato-KatzorFLOTACtechniquewasmeasuredandaveraged(Table1andFigure2).
ForduplicateKato-Katzthicksmearsthestepswereasfol-lows:(K1)labelingduplicatemicroscopeslideswithspe-cificIDandpreparationofduplicateKato-Katzthicksmears;(K2)quantitativemicroscopicreadingofdupli-cateKato-Katzthicksmearsforhookwormeggs;(K3)quantitativemicroscopicreadingofduplicateKato-KatzthicksmearsforA.
lumbricoidesandT.
trichiuraeggs;(K4)dataentry(children'sname,age,sexandschoolgrade);(K5)dataentry(resultsfromallKato-Katzthicksmearreadings);and(K6)washingandpreparingmate-rialsforthenextday.
FortheFLOTACtechniquethefollowingstepswereincluded:(F1)weighing~1gofstoolandhomogeniza-tionin10mlof5%formaldehyde;(F2)filteringhomo-genizedstoolandtransferintotwo15-mlFalcontubeslabeledwithpersonalID;(F3)centrifugationofFalcontubes,discardingsupernatantandfillingFS4intotubes;(F4)assemblyofFLOTACapparatus;(F5)fillingeachchamberoftheFLOTACapparatuswiththehomoge-nizedstoolsuspension(pelletandFS4)fromoneofthetwoFalcontubes;(F6)centrifugationandtranslationofFigure1Flowchartvisualizingthedeterminationofthetotalcostsforonestoolexaminationinanepidemiologicalsurveyonsoil-transmittedhelminthinfections.
Speichetal.
Parasites&Vectors2010,3:71http://www.
parasitesandvectors.
com/content/3/1/71Page4of11FLOTACapparatus;(F7)readingchamber1ofFLO-TACapparatusquantitativelyforA.
lumbricoides,hook-wormandT.
trichiuraeggs;(F8)readingchamber2ofFLOTACapparatusquantitativelyforA.
lumbricoides,hookwormandT.
trichiuraeggs;(F9)dataentry(chil-dren'sname,age,sexandschoolgrade);(F10)dataentry(resultsfromallFLOTACreadings);and(F11)washingandpreparingmaterialsforthenextday.
ThetimetoprepareandreadasingleKato-Katzthicksmearwasassessedasfollows:(K1a)thetimeneededtolabelduplicatemicroscopeslideswasdividedby2(Table1);(K1b)thetimetoprepareasingleKato-Katzthicksmearwasdirectlymeasured;(K2),(K3)and(K5)theaveragetimeoftheworkingstepswasdividedby2;(K6d-j)thetimewasequalforsingleorduplicateKato-Katzthicksmears;(K11a-c)thetimewasdividedby2.
ThetimetoprepareandreadtheFLOTACdoubletech-niquewasassessedasfollows:(F2c),(F3-F6),(F10)and(F11b-e)theaveragetimewasdividedby2;(F8)thisworkingstepwasexcluded.
IntheremainingworkingstepsthemeasuredtimewasapplicablefortheFLOTACdualordoubletechnique.
TocalculatethetotaltimeexpenditureforasingleandduplicateKato-KatzthicksmearsandtheFLOTACdualanddoubletechnique,thearithmeticmeansofthetimeneededtoperformaspecificworkingstepwereFigure2Time(min:sec)toperformduplicateKato-KatzthicksmearsortheFLOTACdualtechniqueinanepidemiologicalsurveyonsoil-transmittedhelminthinfections.
Theareaofeachsegmentofthecirclesisproportionaltotheamountoftimeusedineachworkingstep.
S1:Drivingtoschool.
S2:Distributionofpre-labeledstoolcontainer,andcollectionofstoolsamples.
S3:Drivingtolaboratory.
K1:LabelingmicroscopeslidesandpreparingduplicateKato-Katzthicksmears.
K2:QuantitativemicroscopicreadingforhookwormeggsK3:QuantitativemicroscopicreadingforA.
lumbricoidesandT.
trichiuraeggs.
K4/F9:Dataentry(name,age,sexandschoolgrade).
K5/F10:Dataentry(eggcountsfromKato-Katz/FLOTAC).
K6/F11:Washingandpreparingmaterialsforthenextday.
F1:Weighting~1gofstoolandhomogenizationin10ml5%formaldehyde.
F2:FilteringhomogenizedstoolandfillingintotwoFalcontubes.
F3:CentrifugationoftheFalcontubes,discardingsupernatantandfillingflotationsolutionsintotubes.
F4:AssemblingoftheFLOTACapparatus.
F5:FillingFLOTACapparatuswithhomogenizedsuspension(pelletandflotationsolution).
F6:CentrifugationandafterwardstranslationofFLOTACapparatus.
F7:Readingchamber1quantitativelyforsoil-transmittedhelmintheggs.
F8:Readingchamber2quantitativelyforsoil-transmittedhelmintheggs.
Speichetal.
Parasites&Vectors2010,3:71http://www.
parasitesandvectors.
com/content/3/1/71Page5of11summed-up.
Outofthetotalworkingtime,itwasdeter-minedhowmanyemployeeswereneededtoperform100stoolexaminationsperday,assumingthatlabora-torystaffwork7hperday.
Subsequently,thetotalsal-arycostsfortheteamwerecalculated.
Thecostsweredividedby100,toobtainthecostsduetosalariesperstoolexamination.
CostsduetomaterialsToestimatethetotalcostsduetomaterials,itwasdif-ferentiatedbetweenthreekindsofmaterials:(i)materi-alsthatcanonlybeusedonce(e.
g.
woodenspatula,wiremesh);(ii)materialsthatcanbereused(e.
g.
micro-scopeslidesandpipettes);and(iii)materialsthathavealonglifeexpectancy(e.
g.
microscopeandcentrifuge).
Thefrequencyofpossiblere-usewasdeterminedinthefieldandlaboratory.
Additionally,theefforttorenderthematerialsre-usablewasaccountedforasaworkingstep(e.
g.
washing).
Thelifedurationofmaterialswithalongerlifeexpectancywasestimatedbyconsultinglaboratoryexpertsandtheliterature.
Forthesematerials,itwasestimatedhowmanydaysperyeartheyweretobeused.
Allmaterials,assetcosts,lifetime,daysinuseandtotalcostsarelistedinTable2.
CostsduetoinfrastructureCostsduetoinfrastructureoriginatedfrom(i)theuseofthelaboratorybuildingforstoolexaminations(e.
g.
rent,tapwaterandelectricity);and(ii)theuseofthecarforstoolcontainerdistributionandcollectioninschools.
Themonthlycostsforthelaboratoryandtheassetcostsforthe4-WDcar,togetherwiththemonthlyexpendi-turesforcarmaintenancewerereportedbytheheadofHCLU.
Thelifeexpectancyofacarwasderivedbycon-sultingWHO-choice[21]andthepetrolcostswereassessedonthespotinZanzibar(averagedieselpriceforMarch-May2009).
One-waysensitivityanalysesAseriesofone-waysensitivityanalyseswereperformedtodeterminetherobustnessofthecostestimationsandtoassesstowhatextentthecostsvaryifaspecificpara-meterchanges[22-24].
WealternatedsingleparameterspertainingtothetotalcostsoftheKato-KatzorFLO-TACtechnique.
ForthescenarioindicatedintheAppendix,thefollowingparameterswereconsidered:(i)salary;(ii)unproductivetime;(iii)costsduetomaterials;(iv)petrolcosts;(v)costsduetoinfrastructure;and(vi)costswithoutcollectionofstoolsamplesinthefield.
ResultsParasitologicalfindingsanddiagnosticsensitivityAmong1,066schoolchildrenscreenedwithduplicateKato-Katzthicksmears,theprevalenceofT.
trichiura,hookwormandA.
lumbricoideswas62.
8%,19.
8%and9.
2%,respectively.
TheFLOTACdoubletechniquewasperformedon343stoolsamplesandrevealedrespectiveprevalencesof67.
1%,11.
7%and10.
2%.
Infectioninten-sities,accordingtoWHOguidelines[25],weremostlylight.
ConsideringthecombinedresultsofstoolsamplesexaminedwithduplicateKato-KatzthicksmearsandtheFLOTACdoubletechniqueasdiagnostic'gold'standard,thesensitivityofduplicateKato-KatzthicksmearsfordetectionofT.
trichiura,hookwormandA.
lumbricoideseggswas88%,81%and68%,respectively.
TherespectivesensitivitiesforFLOTACwere95%,54%and88%.
CostOutcomesCostsduetosalariesIn2009thedailysalaryofanemployeeatHCLUwas,onaverage,US$18.
83(minimum:US$17.
65,maximumUS$22.
18;excludingmanagers'salaries).
Theaverageperson-timeneededtocollectonestoolsampleinthefield,includingtransfertoHCLUwas10minand55sec(10:55min)(Figure2[S1-S3]).
TheaveragetimetoprepareandreadduplicateKato-Katzthicksmearswas16:26min(Figure2[K1-K6])and09:39minforasingleKato-Katzthicksmear,whereasfortheFLOTACdualtechniqueatotalof25:49min(Figure2[F1-F11])andfortheFLOTACdoubletechni-queatotalof17:19minwasrecorded.
Thetotaltimeforonestoolexamination,includingstoolcollectionintheschoolsandtransfertoHCLU,was20:34minforasingleKato-Katzthicksmear,27:21minforduplicateKato-Katzthicksmears,28:14minfortheFLOTACdoubletechniqueand36:44minfortheFLOTACdualtechnique.
Includingthesalaryoftheworkers,thecostsduetosalariesforonestoolexaminationwereUS$1.
25forasingleKato-Katzthicksmear,US$1.
57forduplicateKato-Katzthicksmears,US$1.
64fortheFLOTACdou-bletechniqueandUS$1.
95fortheFLOTACdualtechnique.
CostsduetomaterialsThepricesofallmaterialsusedforstoolexaminationsatHCLUtogetherwithexaminationsandassumptionsabouttheirlifeexpectancy,aresummarizedinTable2.
ThecostsduetomaterialsforsingleorduplicateKato-KatzthicksmearswereUS$0.
03andUS$0.
04,respec-tively.
FortheFLOTACdoubleanddualtechniquethecostsduetomaterialswereUS$0.
26andUS$0.
43,respectively.
CostsduetoinfrastructureThemonthlycostsfortheuseofthelaboratorybuildingwerereportedtobeUS$256.
77.
Assumingthat3,000stoolsampleswereexaminedduring1.
5months(30workingdays),thecostsofthelaboratorybuildingwereUS$0.
13perstoolsample.
The4-WDcarwasboughtin2002forUS$22,000.
WHO-choicesuggestsalifetimefora4-WDcarof8years[21].
ConsideringthatthecarSpeichetal.
Parasites&Vectors2010,3:71http://www.
parasitesandvectors.
com/content/3/1/71Page6of11isinuseat200daysperyear,thecostsperdaywereUS$31.
91(includingmonthlycarmaintenanceofUS$51.
87anddailypetrolconsumptionof15ldiesel).
Assumingthat100stoolsampleswerecollectedperday,thecostspersampleduetothecarwereUS$0.
32.
Hence,thecostsduetoinfrastructurewereUS$0.
45foreachdiagnosticmethodinasurveyof30workingdayswithatotalof3,000stoolsamplescollectedbyaresearchteaminafield-settinglocated~30kmfromthelaboratoryandexaminedbyateamofexperiencedlaboratorytechnicians.
TotalcostsTakingintoaccountthecostsduetosalaries,costsduetomaterialsandcostsduetoinfrastructure,thetotalexpenseswereUS$1.
73forasingleKato-Katzthicksmear,US$2.
06forduplicateKato-Katzthicksmears,US$2.
35fortheFLOTACdoubletechniqueandUS$2.
83fortheFLOTACdualtechnique(Figure3).
One-waysensitivityanalysesTheone-waysensitivityanalysesillustratetheeffectofalternatedcostvariablesonthetotalcostsofeitherdiag-nosticapproach(Table3).
Ifsalariesweredoubled,theincreaseintotalcostforonestoolexaminationrangedfrom68.
9%(FLOTACdualtechnique)to76.
3%(dupli-cateKato-Katzthicksmears).
If30%ofunproductivetimewasaddedtothetotaltimeoflaboratoryworkingsteps,theincreaseintotalcostsrangedfrom11.
9%(sin-gleKato-Katzthicksmear)to18.
4%(FLOTACdualtech-nique).
MaterialcostshadamajorimpactonthetotalcostsoftheFLOTACtechnique,butnotonthetotalcostsoftheKato-Katzmethod:doublingthecostsduetoTable2PriceofmaterialneededforduplicateKato-KatzthicksmearsandtheFLOTACdualtechnique,takingintoaccounttheassetcost,lifetimeanddaysofuseMaterialAssetcost(US$)Presentmaterial(n)Lostmaterial(n)Examinationspermaterial(n)Estimatedlifeexpectancy(years)EstimateddaysinuseperyearPriceperstoolexamination(US$)FLOTACdualtechniqueWoodenspatula0.
020.
02Falcontubes(forstoolpreservation)0.
040.
045%formaldehyde(1l)1.
250.
010.
9%NaClsolution(1l)0.
20<0.
01FS4(NaNO3,1l)12.
110.
13Pasteur-pipettes0.
057169570.
01Falcontubes(forpreparation)0.
04100.
01FilterforFLOTAC9.
7370001,0000.
01FLOTACapparatus29.
511,0000.
03FLOTACapparatus(readingdisk)2.
211000.
02Balance(KernEMBbasicbalance)172.
571050<0.
01Centrifuge(HettichUniversal320)5,865.
4410500.
12Centrifuge(HettichEBA3[secondhand])147.
562500.
01DuplicateKato-KatzthicksmearsCellophanepaper0.
010.
01Wiremesh(3cm2)<0.
01<0.
01Microscopeslide0.
096,00030020<0.
01Kato-Katzkit(templateandplasticspatula)0.
309742048.
70.
01FLOTACdualtechniqueandduplicateKato-KatzthicksmearsGloves0.
01<0.
01Container(120ml)forstoolcollection0.
153,17024912.
730.
01Handtallycounter19.
4310100<0.
01Microscope(OlympusCX21)938.
83101000.
01Speichetal.
Parasites&Vectors2010,3:71http://www.
parasitesandvectors.
com/content/3/1/71Page7of11materialsincreasedthetotalcostsoftheFLOTACdou-bleanddualtechniqueby11.
1%and15.
2%,respectively,whilethetotalcostsfortheKato-Katzmethodincreasedbylessthan2%.
Doublingthecostsduetoinfrastructureraisedthetotalcostforonestoolexaminationintherangeof15.
9%(FLOTACdoubletechnique)to25.
9%(singleKato-Katzthicksmear).
Doublingthepetrolcostsraisedthetotalcostsby5.
3%(FLOTACdualtechnique)to8.
6%(singleKato-Katzthicksmear).
Inascenariowherestoolsamplesarenotcollectedinthefield(costsofcarandfield-workexcluded(Figure2[S1-S3])),thetotalcostsdecreaseintherangeof31.
8%(FLOTACdualtechnique)to56.
8%(singleKato-Katzthicksmear).
Figure3TotalcostsfortheKato-KatzandFLOTACtechniqueforthediagnosisofsoil-transmittedhelminthinfectionsinanepidemiologicalsurveycarriedoutinZanzibarin2009,andtakingintoaccountthecostsduetosalaries,costsduetomaterialsandcostsduetoinfrastructure.
Table3Resultsoftheseriesofone-waysensitivityanalysestoillustratetheimpactofalternatedcostparametersonthetotalcostsoftheKato-KatzandtheFLOTACmethodforthediagnosisofsoil-transmittedhelminthinfectionsCostsinUS$(changein%)ParametertestedSingleKato-KatzthicksmearDuplicateKato-KatzthicksmearsFLOTACdoubletechniqueFLOTACdualtechniqueBaseline1.
732.
062.
352.
83CostsduetosalariesSalariesincreaseby100%2.
99(+72.
3%)3.
64(+76.
3%)3.
99(+69.
8%)4.
78(+68.
9%)30%ofunproductivetimeperworkingstepinthelaboratory1.
94(+11.
9%)2.
41(+16.
8%)2.
72(+15.
8%)3.
35(+18.
4%)CostsduetomaterialsMaterialcostsincreaseby100%1.
76(+1.
7%)2.
10(+1.
9%)2.
61(+11.
1%)3.
26(+15.
2%)CostsduetoinfrastructurePetrolcostsincreaseby100%1.
88(+8.
6%)2.
21(+7.
3%)2.
50(+6.
4%)2.
98(+5.
3%)Infrastructurecostsincreaseby100%2.
18(+25.
9%)2.
51(+21.
8%)2.
80(+19.
2%)3.
28(+15.
9%)OthersStoolsamplesbroughttolaboratorybyparticipants0.
75(-56.
8%)1.
12(-45.
9%)1.
40(-40.
6%)1.
93(-31.
8%)Speichetal.
Parasites&Vectors2010,3:71http://www.
parasitesandvectors.
com/content/3/1/71Page8of11DiscussionThetimerequirementsandcostsforthediagnosisofsoil-transmittedhelminthinfectionsinacross-sectionalepidemiologicalsurvey,usingeithertheKato-Katztech-niqueperformedonfreshstoolsamplesortheFLOTACtechniqueusingpreservedstoolsamples,areconsider-able.
Indeed,inourstudy,thecostsforasingleorduplicateKato-KatzthicksmearswereUS$1.
73andUS$2.
06,respectively.
Asexpected,thecostsfortheFLO-TACtechniquewereevenhigher:US$2.
35fortheFLOTACdoubletechniqueandUS$2.
83fortheFLO-TACdualtechnique.
ThehighercostsoftheFLOTACtechniquearemainlycausedbythelongerpreparationtimeforstoolsamplesandmicroscopicexaminationsinthelaboratory.
PreviousstudieshaveshownthattheFLOTACtechniqueismoresensitivethantheKato-Katzmethodforthediagnosisofsoil-transmittedhel-minthinfections[15-18],andhencehighercostsmightbejustified.
Inthepresentstudy,theFLOTACoutper-formedtheKato-KatzmethodonlyforA.
lumbricoidesandT.
trichiuradiagnosis,butwasseeminglylesssensi-tiveforhookwormdiagnosis,forreasonsreportedelse-where(KnoppS,SpeichB,RinaldiL,MohammedKA,KhamisIS,MohammedAZ,AlbonicoM,RollinsonD,MartiH,CringoliG,UtzingerJ:"DiagnosticaccuracyoftheKato-KatzandFLOTACtechniqueswhenusedforassessinganthelminticdrugefficacy",submitted).
Inviewofthehighcoststocollectasinglestoolsam-pleinthefieldandsubsequentexaminationinthelaboratory,preventivechemotherapywithoutpriordiag-nosis,asadvocatedbyWHOforhigh-riskgroupsinendemicsettingsis,atfirstsight,justified[3,26].
Inendemicsettings,wheremorbiditycontrolisshiftingtoinfectionandtransmissioncontrol,anaccurateassess-mentoftheepidemiologicalsituationisrequiredandrendersdiagnosisnecessary[5,7].
Forevaluatingtheeffi-cacyofroutinelyappliedandnewlydevelopeddrugs,aswellasforindividualpatientmanagement,accuratediagnostictoolsareundoubtedlyneeded[5,7].
When-everdiagnosisforsoil-transmittedhelminthiasisiswar-ranted,ourresultscanbeofvaluetodecisionmakersandscientistsinbudget-planningforepidemiologicalsurveysandtoheadsofdiagnosticlaboratoriesforpatientmanagement.
Itisimportanttonotethatinourstudy,theKato-KatzmethodwasperformedbyrigorouslyadheringtotheWHObenchaids[27].
Indeed,allKato-Katzthicksmearswerereadtwice,first20-40minafterprepara-tionforhookwormand3-6hlaterasecondtimeforA.
lumbricoidesandT.
trichiura.
Whilethisprocedureincreasescosts,itresultsinhighersensitivityoftheKato-KatzmethodandmightexplainthedifferencesinthediagnosticperformanceoftheKato-KatzandFLOTACtechniquescomparedtopreviouscomparativeinvestigations[15-18].
Routinely,however,Kato-Katzthicksmearsarereadonlyonceforthethreecommonsoil-transmittedhelminthspecies,whichsavescosts,butalsodecreasessensitivity.
Moreover,ourdataarederivedfromalargesurvey,wheremanystoolsampleswerecollectedandprocessedsimultaneously.
One-waysensitivityanalysesshowedthatcostsdecreasebymorethan50%if,forexample,indivi-dualpatientsaremanagedathospitalorpublichealthcentrelaboratories,withoutaneedforafieldteamanda4-WDcar.
However,inthoselaboratories,stoolsamplesarenotnecessarilyexaminedinlargenumbers,andhencecostandtimearelikelyhigherthanpresentedhere,duetoeconomyofscaleissues[20].
Ofnote,additionalexpensesforthepatientwillthenarisefromtravelcostsandlossofincomeduetomissedworkinghours[28].
Furthermore,inoursetting,theprevalencesofA.
lumbricoidesandhookwormwerelowandinfectionintensitiesofallsoil-transmittedhelminthspecieswerelight.
Hence,thecountingofhelmintheggsbymicro-scopistswasrelativelyquick.
Insettingswithhigherpre-valenceandinfectionintensities,quantitativemicroscopicexaminationwillbemoretimeconsumingandcostswillrise.
Ofadditionalcostrelevanceisthatsalariesusuallycon-stitutethelargestpartofthetotalservicecosts[29].
OursensitivityanalysisindicatesthatanalterationofsalariesisimpactingmostonthetotalcostsofboththeKato-KatzandFLOTACmethod.
IncontrasttotheKato-Katz,thetotalcostsofFLOTACarealsostronglyinfluencedbyalterationsinmaterialcosts.
Itshouldbenotedthatthecostsformaterialmaintenance(e.
g.
centrifugeandmicroscope),thesourcingofchemicalsandtheadequatedisposalofhazardouschemicalswerenotincludedinourcostcalculations.
Moreover,transferoflargeequipment(e.
g.
centrifuge)andcoststhatmightbeincurredatcus-tomswerenotconsideredinouranalyses.
Highlysetting-specificanddependantoneconomyareinfrastructuralcostsincludingrent,electricityandpetrol.
Inourstudy,thetimetoprepareandmicroscopicallyexamineastoolsampleusingtheFLOTACdoubletech-niquewas17:19min.
Thisresultisinlinewiththetimeof21minreportedinarecentstudy,wheretheFLO-TACtechniquewasappliedforthediagnosisofFasciolahepaticainrats[19].
However,anotherstudyapplyingFLOTACforthediagnosisofnon-humanTrichurisinfectionsrevealedapreparationandreadingtimeofonly09:48min[20].
Ofnote,ourlaboratoryworkerswerenewlytrainedtousetheFLOTACmethodanditislikelythattheymighthaveperformedfasterifthemethodwasbeingappliedroutinely.
Hence,costswouldhavebeensaved.
Ontheotherside,thecostsofmoreSpeichetal.
Parasites&Vectors2010,3:71http://www.
parasitesandvectors.
com/content/3/1/71Page9of11extensivetrainingnecessarytolearntheFLOTACtech-niqueincomparisonwiththesimpletrainingfortheKato-Katzmethodwerenotconsideredinouranalyses.
Anotherpotentialbiasinourstudyisthatthatthelaboratoryworkerswereconstantlysupervisedbyanexternalresearcherandthattheirworkingspeedwasrecorded.
Itishencepossiblethatthestaff'sworkingspeeddifferedfromnormalactivity[29].
Itisalsowidelyacknowledgedthateveryemployeehasunproductivephasesduringanormalworkingday[30].
Toaccountforunproductiveworkingtime,weadded30%ofthetotalmeasuredworkingtimeforallworkingstepsinthelaboratoryinoneofthesensitivityanalyses.
Thisincreasedthetotalcostsofthediagnosticmethodsbyupto18%.
Theworkingstepsinthefield(Figure2,S1-S3)wereexcludedfromthecalculationssinceunpro-ductivetimewasalreadyincludedintherespectivetimemeasurements(timerecordofdeparturefrom,andarri-valat,thelaboratory).
Sinceitiswellknownthatemployeesmakeconsciousandunconsciousbreaksdur-ingtheworkingday[30],weconsiderthecostestima-tionsincluding30%ofunproductiveworkingtimeclosertoreality.
Forthereasonthatinourstudywork-erswereobservedandbecauseunproductivetimewasnotincludedinourbaselinecalculation,ourcostesti-matesareratherconservative.
DespitethatthecostestimatesfortheKato-KatzandFLOTACmethodfromourstudyarenotreadilytrans-ferabletootherepidemiologicalsettingswhereaddi-tionalcostsmightoccur,orcostsmightbesaved,webelievethattheygiveareasonableideaoftheexpensesrelatedtosoil-transmittedhelminthdiagnosisandcanguidescientistsanddecisionmakersinbudgetplanningforepidemiologicalsurveys.
Therealcostsofdiagnosisareofconsiderablerelevancetolarge-scalecontrolpro-grammes,whichoftenneedtobalancethecostsoftreatmentsagainstthecostsofdiagnosis.
Asglobalfundstocontrolsoil-transmittedhelminthinfectionsbecomemorewidelyavailablethiswillbeanincreas-inglyimportantissuetoensurethatcontrolprogrammesarecost-effectiveandsustainable.
AcknowledgementsWearegratefultoallparticipatingchildrenandtheheadmastersofKinyasiniandKilomberoschoolsandwouldliketothankallmembersoftheHCLUandtheMinistryofHealthandSocialWelfarefortheirhelpinthefieldandinthelaboratory.
WeacknowledgethesupportofDr.
Martiforassessingcostsandlifeexpectancyoflaboratorymaterials.
ThisinvestigationreceivedfinancialsupportfromtheCommissionofResearchPartnershipswithDevelopingCountries(throughtheSDC-sponsoredprogram"JeunesChercheurs"toS.
Knopp),theSwissNationalScienceFoundation(projectno.
PPOOB–102883andPPOOB–119129),andtheEuropeanUnion(FP6STREPCONTRASTproject,contractno.
032203).
S.
KnoppwasalsosupportedbytheBurckhardtFoundationBasel(personalstipendforthefinalyearofherPhDstudies).
B.
SpeichreceivedfinancialsupportfromtheSwissTropicalandPublicHealthInstitute(teachingandtraining).
AppendixScenarioofepidemiologicalsurveytoillustratetheeffectofchangingcostparametersonthetotalcostsoftheKato-KatzandFLOTACtechnique.
FrameworkScreeningofstoolsamplesobtainedfrom3,000schoolchildrenforsoil-transmittedhelminthinfectionswithin30workingdays.
Onehundredchildrenarescreenedperday.
Oneworkingdayconsistsofamaximumof7workinghours.
ObjectiveToassesshowmuchthealterationofasingleparametercaninfluencethetotalcostsofasingleorduplicateKato-KatzthicksmearsandoftheFLOTACdoubleordualtechniquefordiagnosingsoil-transmittedhelminths.
MethodInaseriesofone-waysensitivityanalysesitwasestimatedhowthetotalcostsforonestoolexaminationwiththeKato-KatzorFLOTACmethodchangeunderthefollowingassumptions:Costsduetosalaries:-thesalariesofemployeesaredoubled-30%ofunproductiveworkingtimeisaddedtoeachlaboratoryworkingstepCostsduetomaterials:-allmaterialcostsaredoubledCostsduetoinfrastructure:-thepetrolpriceisdoubled-costsofthewholeinfrastructureisdoubledOthers:-stoolsamplesaresubmitteddirectlytoalaboratory(field-relatedcostsfromdrivingtoschoolsandcollectingstoolsamples,aswellasthecostsfora4-WDcarareomitted)Authordetails1DepartmentofEpidemiologyandPublicHealth,SwissTropicalandPublicHealthInstitute,Basel,Switzerland.
2UniversityofBasel,Basel,Switzerland.
3HelminthControlLaboratoryUnguja,MinistryofHealthandSocialWelfare,Zanzibar,UnitedRepublicofTanzania.
4DepartmentofPathologyandAnimalHealth,FacultyofVeterinaryMedicine,UniversityofNaples'FedericoII',RegionalCenterforMonitoringParasites(CREMOPAR)RegioneCampania,Naples,Italy.
5WolfsonWellcomeBiomedicalLaboratories,DepartmentofZoology,NaturalHistoryMuseum,London,UK.
Authors'contributionsBS,SK,KAM,GCandJUdesignedthestudy;BS,SK,KAM,ISK,LR,DRandJUimplementedthestudy;BSmanagedthedata;BS,SKandJUanalysedandinterpretedthedata;BSwrotethefirstdraftofthepaper;SK,KAM,ISK,LR,GC,DRandJUrevisedthemanuscript.
Allauthorsread,andapprovedthemanuscriptpriortosubmissionandassistedwiththefinalrevisionofthemanuscript.
CompetinginterestsG.
CringoliistheinventorandcurrentpatentholderoftheFLOTACapparatus.
IncasethecurrentlyongoingvalidationoftheFLOTACtechniqueforhumanandveterinarydiagnosiswillbesuccessful,themethodwillbelicensedfreeofchargetotheWHOandinterestedpublicnon-commercialresearchcenters.
Noneoftheotherauthorshasanyconflictofinterestconcerningtheworkreportedinthispaper.
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doi:10.
1186/1756-3305-3-71Citethisarticleas:Speichetal.
:ComparativecostassessmentoftheKato-KatzandFLOTACtechniquesforsoil-transmittedhelminthdiagnosisinepidemiologicalsurveys.
Parasites&Vectors20103:71.
SubmityournextmanuscripttoBioMedCentralandtakefulladvantageof:ConvenientonlinesubmissionThoroughpeerreviewNospaceconstraintsorcolorgurechargesImmediatepublicationonacceptanceInclusioninPubMed,CAS,ScopusandGoogleScholarResearchwhichisfreelyavailableforredistributionSubmityourmanuscriptatwww.
biomedcentral.
com/submitSpeichetal.
Parasites&Vectors2010,3:71http://www.
parasitesandvectors.
com/content/3/1/71Page11of11
TheFLOTACtechniqueshowsahighersensitivityforthediagnosisoflight-intensitysoil-transmittedhelminthinfectionsbutisreportedtobemorecomplexandexpensive.
Weassessedthecostsrelatedtothecollection,processingandmicroscopicexaminationofstoolsamplesusingtheKato-KatzandFLOTACtechniquesinanepidemiologicalsurveycarriedoutinZanzibar,Tanzania.
Methods:Wemeasuredthetimeforthecollectionofasinglestoolspecimeninthefield,transfertoalaboratory,preparationandmicroscopicexaminationusingstandardprotocolsfortheKato-KatzandFLOTACtechniques.
Salariesofhealthworkers,lifeexpectancyandassetcostsofmaterials,andinfrastructurecostsweredetermined.
TheaveragecostforasingleorduplicateKato-KatzthicksmearsandtheFLOTACdualordoubletechniquewerecalculated.
Results:TheaveragetimeneededtocollectastoolspecimenandperformasingleorduplicateKato-KatzthicksmearsortheFLOTACdualordoubletechniquewas20minand34sec(20:34min),27:21min,28:14minand36:44min,respectively.
ThetotalcostsforasingleandduplicateKato-KatzthicksmearswereUS$1.
73andUS$2.
06,respectively,andfortheFLOTACdoubleanddualtechniqueUS$2.
35andUS$2.
83,respectively.
Salariesimpactedmostonthetotalcostsofeithermethod.
Conclusions:Thetimeandcostforsoil-transmittedhelminthdiagnosisusingeithertheKato-KatzorFLOTACmethodinepidemiologicalsurveysareconsiderable.
Ourresultscanhelptoguidehealthcaredecisionmakersandscientistsinbudgetplanningandfundingforepidemiologicalsurveys,anthelminthicdrugefficacytrialsandmonitoringofcontrolinterventions.
BackgroundChronicinfectionswithoneorseveralofthecommonsoil-transmittedhelminths,Ascarislumbricoides,Tri-churistrichiuraandthehookworms(Ancylostomaduo-denaleandNecatoramericanus),mightaccountforaglobalburdenof39milliondisability-adjustedlifeyears(DALYs)lostannually[1,2].
School-agedchildreninthedevelopingworldareathighestriskofmorbidityduetosoil-transmittedhelminthiasis.
Inthecurrenteraof'preventivechemotherapy',thatisthelarge-scaleadministrationofanthelminthicdrugstoschool-agedchildrenandotherpopulationsatriskofmorbidity[3],diagnosisisoftenneglectedandcost-effectivenessconsiderationsarenecessary.
Yet,diagnosisisofparamountimportanceforanaccurateassessmentoftheepidemiologicalsituationandburdenofdiseaseestimations,andformonitoringdrugefficacyandphar-macovigilance[4-7].
Inepidemiologicalsurveyspertain-ingtosoil-transmittedhelminthiasis(andintestinal*Correspondence:juerg.
utzinger@unibas.
ch1DepartmentofEpidemiologyandPublicHealth,SwissTropicalandPublicHealthInstitute,Basel,SwitzerlandFulllistofauthorinformationisavailableattheendofthearticleSpeichetal.
Parasites&Vectors2010,3:71http://www.
parasitesandvectors.
com/content/3/1/712010Speichetal;licenseeBioMedCentralLtd.
ThisisanOpenAccessarticledistributedunderthetermsoftheCreativeCommonsAttributionLicense(http://creativecommons.
org/licenses/by/2.
0),whichpermitsunrestricteduse,distribution,andreproductioninanymedium,providedtheoriginalworkisproperlycited.
schistosomiasis),theKato-Katztechnique[8]isawidelyuseddiagnosticapproach[2,9-11].
Indeed,themethodisrelativelystraightforward,requiresminimalequipmentwhichismostlyreusable,andhencethemethodisthoughttobeinexpensive[7,10].
Moreover,theKato-Katzmethodissimpletoapplyandlaboratoryworkerscanbetrainedwithinhalfaday[12].
AdrawbackoftheKato-Katzmethod,however,isitslackofsensitivityfordetectinglight-intensitysoil-transmittedhelminthinfec-tions[9,13].
NewresearchhasrevealedthattherecentlydevelopedFLOTACtechnique[14]showsahighersen-sitivitythanmultipleKato-Katzthicksmearsforthediagnosisofsoil-transmittedhelminthinfections[15-17].
ComparedtotheKato-Katzmethod,theFLOTACisamorecomplicatedtechnique,andhencerequiresbetterequippedlaboratories[18-20]andmoreextensivetrain-ingoflaboratoryworkers.
Here,aneconomicevaluationoftheKato-KatzandFLOTACtechniqueswasperformedwithintheframeofanepidemiologicalsurvey.
Specifically,thecostsrelatedtostoolcollection,transfertothelaboratory,prepara-tionandmicroscopicexaminationofsingleanddupli-cateKato-KatzthicksmearsandtheFLOTACdualordoubletechniqueweredetermined.
Thisinformationisrelevantforresearchersanddiseasecontrolmanagersfortheplanningofepidemiologicalsurveysandthemonitoringandevaluationofsoil-transmittedhel-minthiasiscontrolprogrammes.
MaterialsandmethodsStudyarea,populationandethicalconsiderationsThisstudywascarriedoutonUnguja,thelargestislandbelongingtotheZanzibararchipelagoinTanzania,betweenMarchandMay2009.
ThetwoprimaryschoolsofKinyasiniandKilombero,located26and32kmnorth-eastofZanzibarTown,weretheselectedfieldsites.
LaboratoryexaminationswereconductedintheHelminthControlLaboratoryUnguja(HCLU),inZanzi-barTown.
Thestudywasreadilyembeddedinarando-misedcontrolledtrial,assessingtheefficacyandsafetyoffouranthelminthicdrugregimensagainstT.
trichiuraandothersoil-transmittedhelminths.
Atthebeginningofthestudy,1,066schoolchildrenagedbetween6and20years,werescreenedforsoil-transmittedhelminthinfections(KnoppS,MohammedKA,SpeichB,Hatten-dorfJ,KhamisIS,KhamisAN,StothardJR,RollinsonD,MartiH,UtzingerJ:"AlbendazoleandmebendazoleadministeredaloneorincombinationwithivermectinagainstTrichuristrichiura:arandomizedcontrolledtrial",submitted).
ThestudywasapprovedbytheethicscommitteeofBasel,Switzerland(EKBB;referenceno.
13/09)andtheMinistryofHealthandSocialWelfare(MoHSW)ofZanzibar(referenceno.
ZAMEC/0001/09).
Parentsorlegalguardiansofparticipatingchildrensignedawritteninformedconsentsheet.
Childrenconsentedorallytoparticipate.
Attheendofthestudy,allchildrenattend-ingtheprimaryschoolsofKinyasiniandKilomberoweretreatedwithsingleoraldosesofalbendazole(400mg)andpraziquantel(40mg/kg)freeofcharge.
FieldandlaboratoryproceduresTheheadmastersofKinyasiniandKilomberoprimaryschoolswereinformedaboutthepurposeandproce-duresofthestudy.
Afterhavingobtainedwritteninformedconsentbytheparents/legalguardiansandoralconsentbythechildren,thefieldworkwaslaunched.
Everymorning,startingat07:00hoursatHCLU,stoolcontainersandcollectionshelveswereloadedontoa4-wheeldrive(4-WD)car,andateamconsistingof4-6workersfromHCLUvisitedeitherKinyasiniorKilomberoschools.
Theteamlabeledemptycontainerswithuniqueidentification(ID)num-bers,distributedthesetothechildrenandcollectedfilledcontainersthathadbeendistributedthedaybefore.
Eachday,approximately100childrenwereenrolledandlime-sizedearlymorningstoolsampleswerecollected.
ThefilledcontainersweretransferredtoHCLUwithin2-3handprocessedasfollows.
ImmediatelyafterarrivalatHCLU,duplicateKato-Katzthicksmearsfromeachstoolsamplewerepreparedby2-8membersofHCLU,using41.
7mgtemplates[8].
Afteraclearingtimeof20-40min,eachKato-Katzthicksmearwasexaminedquan-titativelyforhookwormeggsbyoneoffourexperiencedmicroscopists.
Intheafternoon,3-6hafterslideprepara-tion,thethicksmearswerere-examinedbyoneoffouradditionalmicroscopists,whocountedeggsofA.
lumbri-coidesandT.
trichiuraandrecordedthemseparately.
OnceaKato-Katzthicksmearhadbeenprepared,thestoolsamplewasplacedbackintothecollectionshelforderedbyincreasingID.
Athirdofthestoolsampleswastakenandasmallamountofstoolwasweighedto~1gusingaKernbalance(EMBbasicbalance;Ballin-gen-Frommern,Germany)andpreservedinapre-labeledtubecontaining10mlof5%formaldehyde.
Thepreservedstoolsampleswerestoredatroomtempera-tureandexaminedbytheFLOTACtechniquewithin3weeksaftercompletionoftheclinicaltrialinlateMay2009[14].
WhiletechniciansfromHCLUwerealreadyacquaintedwiththeKato-Katztechnique,a3-daytrain-ingcoursewasofferedfortheFLOTACtechnique,facilitatedbytwoexpertsfromtheUniversityofNaples,Italy.
Duringthetraining,theFLOTACdualtechniquewasemployed,usingflotationsolutions4(FS4;sodiumnitrate,NaNO3,specificgravity(s.
g.
)=1.
20)and7(FS7;zincsulfate,ZnSO4·7H2O,s.
g.
=1.
35).
Speichetal.
Parasites&Vectors2010,3:71http://www.
parasitesandvectors.
com/content/3/1/71Page2of11TheindividualstepsforFLOTACpreparationandmicroscopicexaminationofstoolsampleswereper-formedby8-12membersofHCLUandaredetailedinTable1.
PreliminaryresultsshowedthatFS4outper-formedFS7forthediagnosisofsoil-transmittedhel-minths,andhenceFS4wasusedthroughout.
IndividualstoolsampleswerepreparedaccordingtotheFLOTACdualtechnique[14].
Inbrief,~1gofstoolwasequallydistributedtothetwochambersoftheFLOTACappa-ratus,butinsteadofusingtwodifferentflotationsolu-tions,FS4wasappliedinbothchambers.
Hence,thereadingofthechamberswasperformedaccordingtotheFLOTACbasictechnique[14].
CostestimationsToassessthecostsforsingleandduplicateKato-KatzthicksmearsandtheFLOTACdualordoubletechni-que,thefollowingexpensesweredetermined:(i)costsduetosalaries;(ii)costsduetomaterials;and(iii)costsduetoinfrastructure.
Wemadethefollowingassump-tions:screeningof3,000childrenforsoil-transmittedhelminthinfectionsbyanexperiencedresearchteam,Table1WorkingstepsandnumberoftimemeasurementstodeterminethecostsoftheKato-KatzandFLOTACmethodforthediagnosisofsoil-transmittedhelminthsinZanzibarWorkingstepnNumberofmeasurementsaKato-Katz(K-K)measurements(K1a)LabelingofK-Kslides10919*5;2*4;1*6(K1b)PreparationofduplicateK-Kslides137121*1;6*0.
5;5*2;1*3(K2)Microscopymorning34132*1;22*2;22*8;21*4;1*5(K3)Microscopyafternoon39644*1;26*8;24*2;24*4(K6a)WashingofK-Kslides1801*180(K6b)Washingspatulaandtemplate2971*91;1*96;1*110(K6c)Cuttingcellophanepaper821*82(K6d)Cuttingwiremesh2061*206FLOTACmeasurements(F1)Measurementof1gofstoolandhomogenization16829*5;1*6;1*7;1*10(F2a)Filter(inclusivelabeling)3131*1(F2b)Filter(exclusivelabeling)4125*1;4*3;2*2(F2c)LabelingFalcontubes333*6;2*4;1*7(F3)CentrifugationoftubesandfillingwithFS6220*3;1*2(F4)AssemblingFLOTACapparatus2929*1(F5)FillingFLOTACapparatus5555*1(F6)CentrifugationandtranslationofFLOTACapparatus3618*2(F7)Readingfirstchamber120120*1(F8)Readingsecondchamber119119*1(F11a)Washingfilterandbeaker829*1;9*6;1*4;1*7;1*8(F11b)OpeningFLOTACapparatus5233*1;1*2;1*3;1*14(F11c)WashingFLOTACapparatus262*3;1*2;1*4;1*14(F11d)WashingFalcontube2083*4;2*5;1*101;1*84;1*1(F11e)Washingpipettes2009*1;1*105;1*84;1*1Measurementsforbothtechniques(S1-S3)Collectionofstoolsamplesatschool2,921b(K4/F9)Dataentry(demographicdata)131*13(K5/F10)Dataentry(results)4075*22;5*23;3*20;3*9;2*14;1*5;1*15;1*21;1*26(K6f/F11f)Puttingapieceofpaperintoanemptycontainertoalleviatecleaningofcontainer1387*10;1*68(K6g/F11g)Removingstooloutofcontainer(beforecleaning)2604*10;2*36;1*38;1*52;1*58(K6h/F11h)Washingofstoolcontainer(withoutlid)655*10;1*15(K6i/F11i)Washinglid563*10;1*5;1*6;1*15(K6j/F11j)ErasingofIDsfromstoolcontainer29018*10;1*110aInterpretedasfollows:forexample,intheworkingstep"LabelingofK-Kslides"itwasmeasured19timeshowmuchtimewasrequiredtolabel5slides,2timesthetimeforlabeling4slidesandoncethetimeforlabeling6slides.
b2,921stoolsampleswerecollectedin38visitsatschools,wherealwaysadifferentnumberofstoolsampleswascollected.
Speichetal.
Parasites&Vectors2010,3:71http://www.
parasitesandvectors.
com/content/3/1/71Page3of11with100stoolsamplesexaminedperdayinalaboratory(Appendix).
TheflowofcostdeterminationisshowninFigure1.
Allcostsarereportedin2009US$.
CostsduetosalariesToassessthecostsduetosalaries,thesalaryofeachmemberoftheHCLU,accordingtohisorherprofes-sionaldegree,wasdeterminedusingaquestionnaire.
Additionally,thetimeforeachworkingstepinthefieldandinthelaboratorywasmeasuredseveraltimesandaveraged.
Finally,thenumberofemployeeswithaspeci-ficoccupationneededtocollect,processandexamine100stoolsamplesperdayusingtheKato-KatzorFLO-TACtechniquewascalculated.
Forthecollectionofstoolsamplesinthefieldthefol-lowingstepswererecorded:(i)thetimefromdepartureinthelaboratory,schoolvisitandreturntothelabora-tory;(ii)thenumberofpersonnelwhovisitedtheschool;and(iii)thenumberofstoolsamplescollectedperday.
Usingthesedata,theaverageperson-timetocollectonestoolsamplewasestimated.
ThedurationofeachdistinctstepinthelaboratoryneededtoperformtheKato-KatzorFLOTACtechniquewasmeasuredandaveraged(Table1andFigure2).
ForduplicateKato-Katzthicksmearsthestepswereasfol-lows:(K1)labelingduplicatemicroscopeslideswithspe-cificIDandpreparationofduplicateKato-Katzthicksmears;(K2)quantitativemicroscopicreadingofdupli-cateKato-Katzthicksmearsforhookwormeggs;(K3)quantitativemicroscopicreadingofduplicateKato-KatzthicksmearsforA.
lumbricoidesandT.
trichiuraeggs;(K4)dataentry(children'sname,age,sexandschoolgrade);(K5)dataentry(resultsfromallKato-Katzthicksmearreadings);and(K6)washingandpreparingmate-rialsforthenextday.
FortheFLOTACtechniquethefollowingstepswereincluded:(F1)weighing~1gofstoolandhomogeniza-tionin10mlof5%formaldehyde;(F2)filteringhomo-genizedstoolandtransferintotwo15-mlFalcontubeslabeledwithpersonalID;(F3)centrifugationofFalcontubes,discardingsupernatantandfillingFS4intotubes;(F4)assemblyofFLOTACapparatus;(F5)fillingeachchamberoftheFLOTACapparatuswiththehomoge-nizedstoolsuspension(pelletandFS4)fromoneofthetwoFalcontubes;(F6)centrifugationandtranslationofFigure1Flowchartvisualizingthedeterminationofthetotalcostsforonestoolexaminationinanepidemiologicalsurveyonsoil-transmittedhelminthinfections.
Speichetal.
Parasites&Vectors2010,3:71http://www.
parasitesandvectors.
com/content/3/1/71Page4of11FLOTACapparatus;(F7)readingchamber1ofFLO-TACapparatusquantitativelyforA.
lumbricoides,hook-wormandT.
trichiuraeggs;(F8)readingchamber2ofFLOTACapparatusquantitativelyforA.
lumbricoides,hookwormandT.
trichiuraeggs;(F9)dataentry(chil-dren'sname,age,sexandschoolgrade);(F10)dataentry(resultsfromallFLOTACreadings);and(F11)washingandpreparingmaterialsforthenextday.
ThetimetoprepareandreadasingleKato-Katzthicksmearwasassessedasfollows:(K1a)thetimeneededtolabelduplicatemicroscopeslideswasdividedby2(Table1);(K1b)thetimetoprepareasingleKato-Katzthicksmearwasdirectlymeasured;(K2),(K3)and(K5)theaveragetimeoftheworkingstepswasdividedby2;(K6d-j)thetimewasequalforsingleorduplicateKato-Katzthicksmears;(K11a-c)thetimewasdividedby2.
ThetimetoprepareandreadtheFLOTACdoubletech-niquewasassessedasfollows:(F2c),(F3-F6),(F10)and(F11b-e)theaveragetimewasdividedby2;(F8)thisworkingstepwasexcluded.
IntheremainingworkingstepsthemeasuredtimewasapplicablefortheFLOTACdualordoubletechnique.
TocalculatethetotaltimeexpenditureforasingleandduplicateKato-KatzthicksmearsandtheFLOTACdualanddoubletechnique,thearithmeticmeansofthetimeneededtoperformaspecificworkingstepwereFigure2Time(min:sec)toperformduplicateKato-KatzthicksmearsortheFLOTACdualtechniqueinanepidemiologicalsurveyonsoil-transmittedhelminthinfections.
Theareaofeachsegmentofthecirclesisproportionaltotheamountoftimeusedineachworkingstep.
S1:Drivingtoschool.
S2:Distributionofpre-labeledstoolcontainer,andcollectionofstoolsamples.
S3:Drivingtolaboratory.
K1:LabelingmicroscopeslidesandpreparingduplicateKato-Katzthicksmears.
K2:QuantitativemicroscopicreadingforhookwormeggsK3:QuantitativemicroscopicreadingforA.
lumbricoidesandT.
trichiuraeggs.
K4/F9:Dataentry(name,age,sexandschoolgrade).
K5/F10:Dataentry(eggcountsfromKato-Katz/FLOTAC).
K6/F11:Washingandpreparingmaterialsforthenextday.
F1:Weighting~1gofstoolandhomogenizationin10ml5%formaldehyde.
F2:FilteringhomogenizedstoolandfillingintotwoFalcontubes.
F3:CentrifugationoftheFalcontubes,discardingsupernatantandfillingflotationsolutionsintotubes.
F4:AssemblingoftheFLOTACapparatus.
F5:FillingFLOTACapparatuswithhomogenizedsuspension(pelletandflotationsolution).
F6:CentrifugationandafterwardstranslationofFLOTACapparatus.
F7:Readingchamber1quantitativelyforsoil-transmittedhelmintheggs.
F8:Readingchamber2quantitativelyforsoil-transmittedhelmintheggs.
Speichetal.
Parasites&Vectors2010,3:71http://www.
parasitesandvectors.
com/content/3/1/71Page5of11summed-up.
Outofthetotalworkingtime,itwasdeter-minedhowmanyemployeeswereneededtoperform100stoolexaminationsperday,assumingthatlabora-torystaffwork7hperday.
Subsequently,thetotalsal-arycostsfortheteamwerecalculated.
Thecostsweredividedby100,toobtainthecostsduetosalariesperstoolexamination.
CostsduetomaterialsToestimatethetotalcostsduetomaterials,itwasdif-ferentiatedbetweenthreekindsofmaterials:(i)materi-alsthatcanonlybeusedonce(e.
g.
woodenspatula,wiremesh);(ii)materialsthatcanbereused(e.
g.
micro-scopeslidesandpipettes);and(iii)materialsthathavealonglifeexpectancy(e.
g.
microscopeandcentrifuge).
Thefrequencyofpossiblere-usewasdeterminedinthefieldandlaboratory.
Additionally,theefforttorenderthematerialsre-usablewasaccountedforasaworkingstep(e.
g.
washing).
Thelifedurationofmaterialswithalongerlifeexpectancywasestimatedbyconsultinglaboratoryexpertsandtheliterature.
Forthesematerials,itwasestimatedhowmanydaysperyeartheyweretobeused.
Allmaterials,assetcosts,lifetime,daysinuseandtotalcostsarelistedinTable2.
CostsduetoinfrastructureCostsduetoinfrastructureoriginatedfrom(i)theuseofthelaboratorybuildingforstoolexaminations(e.
g.
rent,tapwaterandelectricity);and(ii)theuseofthecarforstoolcontainerdistributionandcollectioninschools.
Themonthlycostsforthelaboratoryandtheassetcostsforthe4-WDcar,togetherwiththemonthlyexpendi-turesforcarmaintenancewerereportedbytheheadofHCLU.
Thelifeexpectancyofacarwasderivedbycon-sultingWHO-choice[21]andthepetrolcostswereassessedonthespotinZanzibar(averagedieselpriceforMarch-May2009).
One-waysensitivityanalysesAseriesofone-waysensitivityanalyseswereperformedtodeterminetherobustnessofthecostestimationsandtoassesstowhatextentthecostsvaryifaspecificpara-meterchanges[22-24].
WealternatedsingleparameterspertainingtothetotalcostsoftheKato-KatzorFLO-TACtechnique.
ForthescenarioindicatedintheAppendix,thefollowingparameterswereconsidered:(i)salary;(ii)unproductivetime;(iii)costsduetomaterials;(iv)petrolcosts;(v)costsduetoinfrastructure;and(vi)costswithoutcollectionofstoolsamplesinthefield.
ResultsParasitologicalfindingsanddiagnosticsensitivityAmong1,066schoolchildrenscreenedwithduplicateKato-Katzthicksmears,theprevalenceofT.
trichiura,hookwormandA.
lumbricoideswas62.
8%,19.
8%and9.
2%,respectively.
TheFLOTACdoubletechniquewasperformedon343stoolsamplesandrevealedrespectiveprevalencesof67.
1%,11.
7%and10.
2%.
Infectioninten-sities,accordingtoWHOguidelines[25],weremostlylight.
ConsideringthecombinedresultsofstoolsamplesexaminedwithduplicateKato-KatzthicksmearsandtheFLOTACdoubletechniqueasdiagnostic'gold'standard,thesensitivityofduplicateKato-KatzthicksmearsfordetectionofT.
trichiura,hookwormandA.
lumbricoideseggswas88%,81%and68%,respectively.
TherespectivesensitivitiesforFLOTACwere95%,54%and88%.
CostOutcomesCostsduetosalariesIn2009thedailysalaryofanemployeeatHCLUwas,onaverage,US$18.
83(minimum:US$17.
65,maximumUS$22.
18;excludingmanagers'salaries).
Theaverageperson-timeneededtocollectonestoolsampleinthefield,includingtransfertoHCLUwas10minand55sec(10:55min)(Figure2[S1-S3]).
TheaveragetimetoprepareandreadduplicateKato-Katzthicksmearswas16:26min(Figure2[K1-K6])and09:39minforasingleKato-Katzthicksmear,whereasfortheFLOTACdualtechniqueatotalof25:49min(Figure2[F1-F11])andfortheFLOTACdoubletechni-queatotalof17:19minwasrecorded.
Thetotaltimeforonestoolexamination,includingstoolcollectionintheschoolsandtransfertoHCLU,was20:34minforasingleKato-Katzthicksmear,27:21minforduplicateKato-Katzthicksmears,28:14minfortheFLOTACdoubletechniqueand36:44minfortheFLOTACdualtechnique.
Includingthesalaryoftheworkers,thecostsduetosalariesforonestoolexaminationwereUS$1.
25forasingleKato-Katzthicksmear,US$1.
57forduplicateKato-Katzthicksmears,US$1.
64fortheFLOTACdou-bletechniqueandUS$1.
95fortheFLOTACdualtechnique.
CostsduetomaterialsThepricesofallmaterialsusedforstoolexaminationsatHCLUtogetherwithexaminationsandassumptionsabouttheirlifeexpectancy,aresummarizedinTable2.
ThecostsduetomaterialsforsingleorduplicateKato-KatzthicksmearswereUS$0.
03andUS$0.
04,respec-tively.
FortheFLOTACdoubleanddualtechniquethecostsduetomaterialswereUS$0.
26andUS$0.
43,respectively.
CostsduetoinfrastructureThemonthlycostsfortheuseofthelaboratorybuildingwerereportedtobeUS$256.
77.
Assumingthat3,000stoolsampleswereexaminedduring1.
5months(30workingdays),thecostsofthelaboratorybuildingwereUS$0.
13perstoolsample.
The4-WDcarwasboughtin2002forUS$22,000.
WHO-choicesuggestsalifetimefora4-WDcarof8years[21].
ConsideringthatthecarSpeichetal.
Parasites&Vectors2010,3:71http://www.
parasitesandvectors.
com/content/3/1/71Page6of11isinuseat200daysperyear,thecostsperdaywereUS$31.
91(includingmonthlycarmaintenanceofUS$51.
87anddailypetrolconsumptionof15ldiesel).
Assumingthat100stoolsampleswerecollectedperday,thecostspersampleduetothecarwereUS$0.
32.
Hence,thecostsduetoinfrastructurewereUS$0.
45foreachdiagnosticmethodinasurveyof30workingdayswithatotalof3,000stoolsamplescollectedbyaresearchteaminafield-settinglocated~30kmfromthelaboratoryandexaminedbyateamofexperiencedlaboratorytechnicians.
TotalcostsTakingintoaccountthecostsduetosalaries,costsduetomaterialsandcostsduetoinfrastructure,thetotalexpenseswereUS$1.
73forasingleKato-Katzthicksmear,US$2.
06forduplicateKato-Katzthicksmears,US$2.
35fortheFLOTACdoubletechniqueandUS$2.
83fortheFLOTACdualtechnique(Figure3).
One-waysensitivityanalysesTheone-waysensitivityanalysesillustratetheeffectofalternatedcostvariablesonthetotalcostsofeitherdiag-nosticapproach(Table3).
Ifsalariesweredoubled,theincreaseintotalcostforonestoolexaminationrangedfrom68.
9%(FLOTACdualtechnique)to76.
3%(dupli-cateKato-Katzthicksmears).
If30%ofunproductivetimewasaddedtothetotaltimeoflaboratoryworkingsteps,theincreaseintotalcostsrangedfrom11.
9%(sin-gleKato-Katzthicksmear)to18.
4%(FLOTACdualtech-nique).
MaterialcostshadamajorimpactonthetotalcostsoftheFLOTACtechnique,butnotonthetotalcostsoftheKato-Katzmethod:doublingthecostsduetoTable2PriceofmaterialneededforduplicateKato-KatzthicksmearsandtheFLOTACdualtechnique,takingintoaccounttheassetcost,lifetimeanddaysofuseMaterialAssetcost(US$)Presentmaterial(n)Lostmaterial(n)Examinationspermaterial(n)Estimatedlifeexpectancy(years)EstimateddaysinuseperyearPriceperstoolexamination(US$)FLOTACdualtechniqueWoodenspatula0.
020.
02Falcontubes(forstoolpreservation)0.
040.
045%formaldehyde(1l)1.
250.
010.
9%NaClsolution(1l)0.
20<0.
01FS4(NaNO3,1l)12.
110.
13Pasteur-pipettes0.
057169570.
01Falcontubes(forpreparation)0.
04100.
01FilterforFLOTAC9.
7370001,0000.
01FLOTACapparatus29.
511,0000.
03FLOTACapparatus(readingdisk)2.
211000.
02Balance(KernEMBbasicbalance)172.
571050<0.
01Centrifuge(HettichUniversal320)5,865.
4410500.
12Centrifuge(HettichEBA3[secondhand])147.
562500.
01DuplicateKato-KatzthicksmearsCellophanepaper0.
010.
01Wiremesh(3cm2)<0.
01<0.
01Microscopeslide0.
096,00030020<0.
01Kato-Katzkit(templateandplasticspatula)0.
309742048.
70.
01FLOTACdualtechniqueandduplicateKato-KatzthicksmearsGloves0.
01<0.
01Container(120ml)forstoolcollection0.
153,17024912.
730.
01Handtallycounter19.
4310100<0.
01Microscope(OlympusCX21)938.
83101000.
01Speichetal.
Parasites&Vectors2010,3:71http://www.
parasitesandvectors.
com/content/3/1/71Page7of11materialsincreasedthetotalcostsoftheFLOTACdou-bleanddualtechniqueby11.
1%and15.
2%,respectively,whilethetotalcostsfortheKato-Katzmethodincreasedbylessthan2%.
Doublingthecostsduetoinfrastructureraisedthetotalcostforonestoolexaminationintherangeof15.
9%(FLOTACdoubletechnique)to25.
9%(singleKato-Katzthicksmear).
Doublingthepetrolcostsraisedthetotalcostsby5.
3%(FLOTACdualtechnique)to8.
6%(singleKato-Katzthicksmear).
Inascenariowherestoolsamplesarenotcollectedinthefield(costsofcarandfield-workexcluded(Figure2[S1-S3])),thetotalcostsdecreaseintherangeof31.
8%(FLOTACdualtechnique)to56.
8%(singleKato-Katzthicksmear).
Figure3TotalcostsfortheKato-KatzandFLOTACtechniqueforthediagnosisofsoil-transmittedhelminthinfectionsinanepidemiologicalsurveycarriedoutinZanzibarin2009,andtakingintoaccountthecostsduetosalaries,costsduetomaterialsandcostsduetoinfrastructure.
Table3Resultsoftheseriesofone-waysensitivityanalysestoillustratetheimpactofalternatedcostparametersonthetotalcostsoftheKato-KatzandtheFLOTACmethodforthediagnosisofsoil-transmittedhelminthinfectionsCostsinUS$(changein%)ParametertestedSingleKato-KatzthicksmearDuplicateKato-KatzthicksmearsFLOTACdoubletechniqueFLOTACdualtechniqueBaseline1.
732.
062.
352.
83CostsduetosalariesSalariesincreaseby100%2.
99(+72.
3%)3.
64(+76.
3%)3.
99(+69.
8%)4.
78(+68.
9%)30%ofunproductivetimeperworkingstepinthelaboratory1.
94(+11.
9%)2.
41(+16.
8%)2.
72(+15.
8%)3.
35(+18.
4%)CostsduetomaterialsMaterialcostsincreaseby100%1.
76(+1.
7%)2.
10(+1.
9%)2.
61(+11.
1%)3.
26(+15.
2%)CostsduetoinfrastructurePetrolcostsincreaseby100%1.
88(+8.
6%)2.
21(+7.
3%)2.
50(+6.
4%)2.
98(+5.
3%)Infrastructurecostsincreaseby100%2.
18(+25.
9%)2.
51(+21.
8%)2.
80(+19.
2%)3.
28(+15.
9%)OthersStoolsamplesbroughttolaboratorybyparticipants0.
75(-56.
8%)1.
12(-45.
9%)1.
40(-40.
6%)1.
93(-31.
8%)Speichetal.
Parasites&Vectors2010,3:71http://www.
parasitesandvectors.
com/content/3/1/71Page8of11DiscussionThetimerequirementsandcostsforthediagnosisofsoil-transmittedhelminthinfectionsinacross-sectionalepidemiologicalsurvey,usingeithertheKato-Katztech-niqueperformedonfreshstoolsamplesortheFLOTACtechniqueusingpreservedstoolsamples,areconsider-able.
Indeed,inourstudy,thecostsforasingleorduplicateKato-KatzthicksmearswereUS$1.
73andUS$2.
06,respectively.
Asexpected,thecostsfortheFLO-TACtechniquewereevenhigher:US$2.
35fortheFLOTACdoubletechniqueandUS$2.
83fortheFLO-TACdualtechnique.
ThehighercostsoftheFLOTACtechniquearemainlycausedbythelongerpreparationtimeforstoolsamplesandmicroscopicexaminationsinthelaboratory.
PreviousstudieshaveshownthattheFLOTACtechniqueismoresensitivethantheKato-Katzmethodforthediagnosisofsoil-transmittedhel-minthinfections[15-18],andhencehighercostsmightbejustified.
Inthepresentstudy,theFLOTACoutper-formedtheKato-KatzmethodonlyforA.
lumbricoidesandT.
trichiuradiagnosis,butwasseeminglylesssensi-tiveforhookwormdiagnosis,forreasonsreportedelse-where(KnoppS,SpeichB,RinaldiL,MohammedKA,KhamisIS,MohammedAZ,AlbonicoM,RollinsonD,MartiH,CringoliG,UtzingerJ:"DiagnosticaccuracyoftheKato-KatzandFLOTACtechniqueswhenusedforassessinganthelminticdrugefficacy",submitted).
Inviewofthehighcoststocollectasinglestoolsam-pleinthefieldandsubsequentexaminationinthelaboratory,preventivechemotherapywithoutpriordiag-nosis,asadvocatedbyWHOforhigh-riskgroupsinendemicsettingsis,atfirstsight,justified[3,26].
Inendemicsettings,wheremorbiditycontrolisshiftingtoinfectionandtransmissioncontrol,anaccurateassess-mentoftheepidemiologicalsituationisrequiredandrendersdiagnosisnecessary[5,7].
Forevaluatingtheeffi-cacyofroutinelyappliedandnewlydevelopeddrugs,aswellasforindividualpatientmanagement,accuratediagnostictoolsareundoubtedlyneeded[5,7].
When-everdiagnosisforsoil-transmittedhelminthiasisiswar-ranted,ourresultscanbeofvaluetodecisionmakersandscientistsinbudget-planningforepidemiologicalsurveysandtoheadsofdiagnosticlaboratoriesforpatientmanagement.
Itisimportanttonotethatinourstudy,theKato-KatzmethodwasperformedbyrigorouslyadheringtotheWHObenchaids[27].
Indeed,allKato-Katzthicksmearswerereadtwice,first20-40minafterprepara-tionforhookwormand3-6hlaterasecondtimeforA.
lumbricoidesandT.
trichiura.
Whilethisprocedureincreasescosts,itresultsinhighersensitivityoftheKato-KatzmethodandmightexplainthedifferencesinthediagnosticperformanceoftheKato-KatzandFLOTACtechniquescomparedtopreviouscomparativeinvestigations[15-18].
Routinely,however,Kato-Katzthicksmearsarereadonlyonceforthethreecommonsoil-transmittedhelminthspecies,whichsavescosts,butalsodecreasessensitivity.
Moreover,ourdataarederivedfromalargesurvey,wheremanystoolsampleswerecollectedandprocessedsimultaneously.
One-waysensitivityanalysesshowedthatcostsdecreasebymorethan50%if,forexample,indivi-dualpatientsaremanagedathospitalorpublichealthcentrelaboratories,withoutaneedforafieldteamanda4-WDcar.
However,inthoselaboratories,stoolsamplesarenotnecessarilyexaminedinlargenumbers,andhencecostandtimearelikelyhigherthanpresentedhere,duetoeconomyofscaleissues[20].
Ofnote,additionalexpensesforthepatientwillthenarisefromtravelcostsandlossofincomeduetomissedworkinghours[28].
Furthermore,inoursetting,theprevalencesofA.
lumbricoidesandhookwormwerelowandinfectionintensitiesofallsoil-transmittedhelminthspecieswerelight.
Hence,thecountingofhelmintheggsbymicro-scopistswasrelativelyquick.
Insettingswithhigherpre-valenceandinfectionintensities,quantitativemicroscopicexaminationwillbemoretimeconsumingandcostswillrise.
Ofadditionalcostrelevanceisthatsalariesusuallycon-stitutethelargestpartofthetotalservicecosts[29].
OursensitivityanalysisindicatesthatanalterationofsalariesisimpactingmostonthetotalcostsofboththeKato-KatzandFLOTACmethod.
IncontrasttotheKato-Katz,thetotalcostsofFLOTACarealsostronglyinfluencedbyalterationsinmaterialcosts.
Itshouldbenotedthatthecostsformaterialmaintenance(e.
g.
centrifugeandmicroscope),thesourcingofchemicalsandtheadequatedisposalofhazardouschemicalswerenotincludedinourcostcalculations.
Moreover,transferoflargeequipment(e.
g.
centrifuge)andcoststhatmightbeincurredatcus-tomswerenotconsideredinouranalyses.
Highlysetting-specificanddependantoneconomyareinfrastructuralcostsincludingrent,electricityandpetrol.
Inourstudy,thetimetoprepareandmicroscopicallyexamineastoolsampleusingtheFLOTACdoubletech-niquewas17:19min.
Thisresultisinlinewiththetimeof21minreportedinarecentstudy,wheretheFLO-TACtechniquewasappliedforthediagnosisofFasciolahepaticainrats[19].
However,anotherstudyapplyingFLOTACforthediagnosisofnon-humanTrichurisinfectionsrevealedapreparationandreadingtimeofonly09:48min[20].
Ofnote,ourlaboratoryworkerswerenewlytrainedtousetheFLOTACmethodanditislikelythattheymighthaveperformedfasterifthemethodwasbeingappliedroutinely.
Hence,costswouldhavebeensaved.
Ontheotherside,thecostsofmoreSpeichetal.
Parasites&Vectors2010,3:71http://www.
parasitesandvectors.
com/content/3/1/71Page9of11extensivetrainingnecessarytolearntheFLOTACtech-niqueincomparisonwiththesimpletrainingfortheKato-Katzmethodwerenotconsideredinouranalyses.
Anotherpotentialbiasinourstudyisthatthatthelaboratoryworkerswereconstantlysupervisedbyanexternalresearcherandthattheirworkingspeedwasrecorded.
Itishencepossiblethatthestaff'sworkingspeeddifferedfromnormalactivity[29].
Itisalsowidelyacknowledgedthateveryemployeehasunproductivephasesduringanormalworkingday[30].
Toaccountforunproductiveworkingtime,weadded30%ofthetotalmeasuredworkingtimeforallworkingstepsinthelaboratoryinoneofthesensitivityanalyses.
Thisincreasedthetotalcostsofthediagnosticmethodsbyupto18%.
Theworkingstepsinthefield(Figure2,S1-S3)wereexcludedfromthecalculationssinceunpro-ductivetimewasalreadyincludedintherespectivetimemeasurements(timerecordofdeparturefrom,andarri-valat,thelaboratory).
Sinceitiswellknownthatemployeesmakeconsciousandunconsciousbreaksdur-ingtheworkingday[30],weconsiderthecostestima-tionsincluding30%ofunproductiveworkingtimeclosertoreality.
Forthereasonthatinourstudywork-erswereobservedandbecauseunproductivetimewasnotincludedinourbaselinecalculation,ourcostesti-matesareratherconservative.
DespitethatthecostestimatesfortheKato-KatzandFLOTACmethodfromourstudyarenotreadilytrans-ferabletootherepidemiologicalsettingswhereaddi-tionalcostsmightoccur,orcostsmightbesaved,webelievethattheygiveareasonableideaoftheexpensesrelatedtosoil-transmittedhelminthdiagnosisandcanguidescientistsanddecisionmakersinbudgetplanningforepidemiologicalsurveys.
Therealcostsofdiagnosisareofconsiderablerelevancetolarge-scalecontrolpro-grammes,whichoftenneedtobalancethecostsoftreatmentsagainstthecostsofdiagnosis.
Asglobalfundstocontrolsoil-transmittedhelminthinfectionsbecomemorewidelyavailablethiswillbeanincreas-inglyimportantissuetoensurethatcontrolprogrammesarecost-effectiveandsustainable.
AcknowledgementsWearegratefultoallparticipatingchildrenandtheheadmastersofKinyasiniandKilomberoschoolsandwouldliketothankallmembersoftheHCLUandtheMinistryofHealthandSocialWelfarefortheirhelpinthefieldandinthelaboratory.
WeacknowledgethesupportofDr.
Martiforassessingcostsandlifeexpectancyoflaboratorymaterials.
ThisinvestigationreceivedfinancialsupportfromtheCommissionofResearchPartnershipswithDevelopingCountries(throughtheSDC-sponsoredprogram"JeunesChercheurs"toS.
Knopp),theSwissNationalScienceFoundation(projectno.
PPOOB–102883andPPOOB–119129),andtheEuropeanUnion(FP6STREPCONTRASTproject,contractno.
032203).
S.
KnoppwasalsosupportedbytheBurckhardtFoundationBasel(personalstipendforthefinalyearofherPhDstudies).
B.
SpeichreceivedfinancialsupportfromtheSwissTropicalandPublicHealthInstitute(teachingandtraining).
AppendixScenarioofepidemiologicalsurveytoillustratetheeffectofchangingcostparametersonthetotalcostsoftheKato-KatzandFLOTACtechnique.
FrameworkScreeningofstoolsamplesobtainedfrom3,000schoolchildrenforsoil-transmittedhelminthinfectionswithin30workingdays.
Onehundredchildrenarescreenedperday.
Oneworkingdayconsistsofamaximumof7workinghours.
ObjectiveToassesshowmuchthealterationofasingleparametercaninfluencethetotalcostsofasingleorduplicateKato-KatzthicksmearsandoftheFLOTACdoubleordualtechniquefordiagnosingsoil-transmittedhelminths.
MethodInaseriesofone-waysensitivityanalysesitwasestimatedhowthetotalcostsforonestoolexaminationwiththeKato-KatzorFLOTACmethodchangeunderthefollowingassumptions:Costsduetosalaries:-thesalariesofemployeesaredoubled-30%ofunproductiveworkingtimeisaddedtoeachlaboratoryworkingstepCostsduetomaterials:-allmaterialcostsaredoubledCostsduetoinfrastructure:-thepetrolpriceisdoubled-costsofthewholeinfrastructureisdoubledOthers:-stoolsamplesaresubmitteddirectlytoalaboratory(field-relatedcostsfromdrivingtoschoolsandcollectingstoolsamples,aswellasthecostsfora4-WDcarareomitted)Authordetails1DepartmentofEpidemiologyandPublicHealth,SwissTropicalandPublicHealthInstitute,Basel,Switzerland.
2UniversityofBasel,Basel,Switzerland.
3HelminthControlLaboratoryUnguja,MinistryofHealthandSocialWelfare,Zanzibar,UnitedRepublicofTanzania.
4DepartmentofPathologyandAnimalHealth,FacultyofVeterinaryMedicine,UniversityofNaples'FedericoII',RegionalCenterforMonitoringParasites(CREMOPAR)RegioneCampania,Naples,Italy.
5WolfsonWellcomeBiomedicalLaboratories,DepartmentofZoology,NaturalHistoryMuseum,London,UK.
Authors'contributionsBS,SK,KAM,GCandJUdesignedthestudy;BS,SK,KAM,ISK,LR,DRandJUimplementedthestudy;BSmanagedthedata;BS,SKandJUanalysedandinterpretedthedata;BSwrotethefirstdraftofthepaper;SK,KAM,ISK,LR,GC,DRandJUrevisedthemanuscript.
Allauthorsread,andapprovedthemanuscriptpriortosubmissionandassistedwiththefinalrevisionofthemanuscript.
CompetinginterestsG.
CringoliistheinventorandcurrentpatentholderoftheFLOTACapparatus.
IncasethecurrentlyongoingvalidationoftheFLOTACtechniqueforhumanandveterinarydiagnosiswillbesuccessful,themethodwillbelicensedfreeofchargetotheWHOandinterestedpublicnon-commercialresearchcenters.
Noneoftheotherauthorshasanyconflictofinterestconcerningtheworkreportedinthispaper.
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