rapid tests for diagnosing syphilis

8/12/2019 Rapid Tests for Diagnosing Syphilis

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Rapid tests for diagnosing syphilis:validation in an STD clinic in the AmazonRegion, Brazil

Testes rpidos para diagnstico de sfilis:valida!o em clnica de DST na Regi!oAmaz"nica, Brasil

Adele Sch#artz Benza$en%& 'nri()e *al+n *arca%%& os-.arlos *omes Sardinha%& o!o .atarino D)tra )nior%&

Rosanna /eeling

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IFundao de Dermatologia Tropical e Venereologia Alfredo daMatta, Manaus, BrasilIIUniversidad Calito !arcia, "avana, Cu#aIII$orld "ealt% &rgani'ation, !eneva, ()it'erland

Correspondence

ABSTRA.T

Correct, earl* diagnosis and treatment of s*p%ilis are essential forits control+ Traditional diagnostic tests depend on speciali'edeuipment, installations, and %uman resources+ In t%e searc% foruic-, simple tests, a pro.ect )as conducted on t%e validation andreproduci#ilit* of four different tests, previousl* assessed #* $"&reference la#oratories+ T%e stud* also verified t%e operationalc%aracteristics and acceptance #* patients and %ealt%professionals+ (amples o#tained at an (TD clinic )ere from /01and 203 patients )it% /1 and /2 positive results according toFTA4A#s 5gold standard6 in studies 1 and 2, respectivel*+ T%esensitivit* varied from 30 to 789, specificit* )as greater t%an739, and ::V )as ; 79 and -appainde


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R'S012

& diagn@stico e o tratamento corretos e precoces da sfilis soessenciais para o seu controle+ &s testes diagn@sticos tradicionaisdependem de euipamentos, instalaes e recursos %umanosespeciali'ados+ a #usca de testes de eecuo simplificada e

rpida, reali'ou4se pro.eto de validao e da reproduti#ilidade deuatro diferentes testes anteriormente avaliados pelosla#orat@rios de referEncia da &rgani'ao Mundial da (ade+Verificaram4se tam#Gm as caractersticas operacionais eaceita#ilidade dos pacientes e dos profissionais de sade+ Asamostras o#tidas numa clnica de D(T constaram de /01 e 203pacientes com /1 e /2 positivos no FTA4A#s 5padro ouro6 nosestudos 1 e 2, respectivamente+ A sensi#ilidade variou entre 30 e789, especificidade superior a 739 e valor preditivo positivo ;79 e +

Fetal deat%s and mor#idit* t%roug% congenital s*p%ilis can #eprevented if identified and treated adeuatel* in t%e mot%ersinfected #efore t%e #eginning of t%e t%ird trimester+ evert%eless,unfortunatel*, t%e ma.orit* of pregnant )omen infected #*s*p%ilis are as*mptomatic and it is onl* possi#le to identif* t%emif t%e* are included in programs of prevention and control andperform serological tests+

In t%e case of adults, t%e algorit%ms designed to managegenital ulcer s*ndrome include s*p%ilis as one of t%e mostpro#a#le causes, ma-ing possi#le a proper treatment of t%ispat%olog*+ Mean)%ile, most of t%e time, patients are totall*


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as*mptomatic and, not #eing diagnosed correctl*, are nottreated, and %ave important complications related to gestationand c%ild#irt%, facilitating t%e seual transmission of "IV 3,7+

Man* developed countries %ave esta#lis%ed trac-ing activitiesin t%eir s*p%ilis control programs+ T%e* %ave #een using tests

called nontreponemal tests, li-e t%e Venereal Disease =esearc%Ha#orator* 5VD=H6 and t%e =apid :lasma =eagent test 5=:=6+Aside from #eing eas* to carr* out, t%eir lo) cost, and t%eirrelativel* rapid results, t%e* cannot #e applied in all t%e countr*Jsprimar* %ealt% care units in virtue of t%e fact t%e* reuirerefrigeration or ot%er la#orator* facilities li-e electricit*, or acentrifuge, for eample+ Toget%er )it% t%ese factors, )%en t%esetests are emplo*ed, principall* on pregnant )omen, up to 239percent of positive results are #iologicall* false reactions and+even in ideal conditions reuire additional tests of greaterspecificit* 5treponemal tests, suc% as t%e fluorescent treponemalanti#od* a#sorption test4FTA4A#s, t%e micro%emagglutination testand %emoagglutination test for Treponema pallidum anti#odies4T:"A, etc+6 1,1


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After)ards, in t%e *ear 2


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Q T%e participating patients )ere recruited from among t%ose )%opresented t%emselves at t%e speciali'ed (TD clinic in a voluntar*and consecutive manner, starting on Marc% 1, 2


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maimum accepta#le error of 9 and /9 in eac% of t%e samples,respectivel*+

Q For validation of t%e tests, sensitivit*, specificit*, positivepredictive value 5::V6, and negative predictive value 5:V6 )erecalculated )it% t%eir respective confidence interval of 7/9

57/9CI6+ To evaluate t%e reproduci#ilit* of eac% test, glo#alagreement rates and -appa indices )ere emplo*ed+ Toinvestigate t%e eistence of statisticall* significant differences#et)een t%e validation results for eac% test, c%i4suare tests forproportional differences )ere carried out 5)it% Xates correction6+

Q To get opinions a#out t%e operational ualities of eac% test anopinion uestionnaire )as created and filled out #* t%e 1professionals responsi#le for t%e eecution of rapid testevaluations+

Res)lts

T%e validation of t%e tests )as carried out in t)o differenttime stages in distinct samples of patients, eac% of t%em used toevaluate a pair of tests+ T%e comparison of t%e validation results,t%erefore, cannot #e etended to t%e four tests toget%er and onl*can #e referred to #* separate pairs, denominated studies 1 and2+ T%e same professionals )or-ed on all four tests,minimi'ingstatistical #ias+

In t%e first stud* to validate t%e tests (*p%ic%ec-4$B and (DBioline (*p%ilis, a total of /01 consecutive patients )ere studiedduring t%e period from Marc% 1 t%roug% Rune 10, 2


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T%e epidemiological varia#les of t%e patients included in t%esamples under anal*sis and t%e la#orator* results of t%e t)ostudies )ere recorded on registration forms and in t%e la#orator*ledgers+

T%e reproduci#ilit* of t%e tests, )%en done #* t%e pro.ectteams 5patient care team and la#orator* team6 )ere evaluatedt%roug% t%e percentage of agreement and t%e -appa coefficient+For t%e purpose of t%is stud* )%en t%ese indicators %ad values ofmore t%an


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In #ot% t%e studies, t%e four rapid tests )ere compared )it%t%e FTA4A#s and t%e VD=H 5routinel* emplo*ed in %ealt% service6+T%e tests carried out #* t%e professionals )or-ing in t%e clinic)ere compared to t%ose carried out in t%e la#orator* #*professionals more eperienced in t%is t*pe of )or- 5Ta#le 6+

T%e validation of sensitivit* compared to FTA4A#s s%o)edt%at in stud* 1 (D Bioline (*p%ilis 533+29 and 7


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#* t%e la#orator* team, emplo*ing for t%is t%e overall agreementindicators, or t%e percentage of agreement or t%e -appa inde+

T%e reproduci#ilit* ac%ieved #* t%e (D Bioline (*p%ilis and(*p%ic%ec-4$B proved ecellent )%en eecuted #* #ot% teams,)it% agreement values of 779 and -appa inde ; +79 and7>+79, and V::s of 729 and 729 )%en carried out #* #ot%teams+

T%e 7/9CI for t%e sensitivit* value of VisiTect (*p%ilis )%encarried out #* t%e la#orator* team )as found to #e #et)een 3/+>and 77+, surpassing t%at of Determine (*p%ilis T: )it% #et)een>/+7 and 7/+2, respectivel*+ A c%i4suare test for proportiondifferences p 376+ $%enas-ed %o) long t%e* )ere )illing to )ait, 1


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an %our, and 9 up to t)o %ours, %o)ever as t%e average )aitfor test results )as 1/ minutes 5#et)een 1< and 2< minutes6, it)as confirmed t%at more t%an 7


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In stud* 1, t%e (D Bioline (*p%ilis presented a sensitivit*57


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T%e mean point value o#tained in Manaus 578+296 )as muc%%ig%er t%an t%e mean of t%e (DI studies 53/96, and )as also%ig%er t%an t%ose o#tained in t%e eig%t studies? on t%e ot%er%and, t%e specificities )ere ver* similar 573+/9 and 7396+

Determine Syphilis T/

In Manaus, t%e value o#tained 533+/96 )as lo)er t%an t%emean of t%e (DI stud* 57>+296, onl* #eing similar to t%ato#tained in Birming%am 5U+P6+ T%e specificit* )as %ig%er in t%eBra'ilian cit* 57>+796, compared to t%e (DI mean 570+1796+

T%e Determine (*p%ilis T: )as also recentl* evaluated in a.oint stud* carried out #* t%e CDC, t%e :an American "ealt%&rgani'ationL$"&, and t%e Instituto Kvandro C%agas e Instituto&s)lado Cru' Kvandro C%agas Institute and &s)aldo Cru'InstituteW in Bra'il 1>, #eing interpreted #* t%ree differento#servers+ T%e sensitivit* in relation to t%e gold standard

emplo*ed 5T:"A6 varied #et)een 7/+89 and 739, )%ic% )ere%ig%er t%an t%ose encountered in Manaus+ T%e specificit*, on t%eot%er %and, varied #et)een 7/+>9 and 7>+9, a similar gradientto t%e one made evident #* t%e present researc%+

Anot%er stud* of Determine (*p%ilis T:, carried out in (o:aulo, Bra'il 5Instituto Adolfo Hut'LAdolfo Hut' Institute6, found asensitivit* of 7+89, a specificit* of 72+/9, and a V:: of 7/+29)%en compared to FTA4A#s and t%e T:"A 13+

A more pronounced difference )as o#served #et)een t%eresults of different validations carried out in reference to t%eVisiTect (*p%ilis test )%ic% s%o)ed a %ig%er sensitivit* in Manaus)%en compared to t%e results o#tained in t%e eig%t (DIla#oratories+

T%e prevalence of positive cases in t%e sample su#mitted int%e first (DI stud* )as %ig%er 5around /


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VisiTect (*p%ilis test, t%is last one %ad a stisticall* significant%ig%er sensivit*, possi#l* due to variations of temperature and%umidit* )%ic% are ver* %ig% in t%e Bra'ilian cit*, possi#l*causing alterations in t%e strip of Determine (*p%ilis T: 5t%e onl*one of t%e four tests )%ic% uses suc% strips6+ T%is %*pot%esiss%ould #e verified in t%e future+

Anot%er element t%at s%ould al)a*s #e remem#ered is t%at apositive result of an* one of t%ese rapid tests 5as also occurs )it%ot%er treponemic tests6 does not necessaril* mean a recent oractive infection+ T%is is a negative factor for t%eir use as atrac-ing test in areas of %ig% prevalence )%ere t%ere are man*people t%at %ave alread* %ad s*p%ilis and %ave #een treated andcured of it and )ill still test positive )it% rapid tests+ T%is impliest%e additional use of t%e tests currentl* used, VD=H or =:=, )it%titration, to avoid unnecessar* treatment+

Finall*, it )as s%o)n t%at more t%an 7


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Development :rogrammeL$orld Ban-L$orld "ealt% &rgani'ation(pecial :rogramme for =esearc% and Training in TropicalDiseases, and for t%e suggestions :rof+ Dr+ Adauto Ara.o andDra+ Hui'a "arunari Matida+

References

1+ :eeling =$, "tun Xe+ Diagnostic tools for preventing andmanagement maternal and congenital s*p%ilis and overvie)+ Bull$orld "ealt% &rgan 2


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11+ T%e (euall* Transmitted Diseases DiagnosticsInitiativeL(pecial :rogramme for =esearc% and Training inTropical Diseases+ Ha#orator*4#ased evaluation of rapid s*p%ilisdiagnostics+ =esults from 3 (DI (ites+ !eneva T%e (euall*Transmitted Diseases Diagnostics InitiativeL(pecial :rogrammefor =esearc% and Training in Tropical Diseases? 2


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=ua Coda.s 20, Manaus, AM 87

rapid tests for diagnosing syphilis

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