Agreement Between Enzyme Linked Immunosorbent Assay with Rapid Plasma Reagin and Treponemapallidumhaem Agglutination Assay for Screening and Diagnosis of Syphilis at National Blood Bank Service in Addis Ababa, Ethiopia
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Date
2016-08
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Addis Ababa University
Abstract
Background: Serological diagnosis of syphilis is based on demonstration of specific treponemalantibody and non treponemal antibodies (reagin) in body fluids. Accurate and reliable testing is acritical step in ensuring the diagnosis of syphilis and the safety of blood transfusion service.Performance agreement between syphilis tests is not documented well in Ethiopia.
Objectives: To determine agreement between Enzyme Linked Immunosorbent Assay with RapidPlasma Reagin and TreponemapallidumHaemagglutination Assay for screening and diagnosis ofsyphilis.
Methods:Laboratory based Cross sectional study was carried out from January 2016 to June2016 at National Blood Bank Service Addis Ababa, Ethiopia. All positive (One hundred andninety) and 190 negative samples were used which stored in NBBS (National Blood BankService) laboratory from July 2015 to Dec 2015 (total 380 samples). Systematic randomsampling method was used to select negative samples .The data was analyzed by SPSS version20 software. The percentage agreement and κ value were compared; the sensitivity, specificity,positive predictive value and negative predictive value of the ELISA and RPR were calculated. Pvalue less than 0.05 were taken as statistical significant.
Results:From 190 ELISA positive sera, 151 (80%) were confirmed as positive by TPHA, 39 (20%) were found to be false positive. 59 (39%) of samples were positive and 92 (61%) were falsenegative by RPR. From 190 ELISA negative sera all were negative by RPR and TPHA. Thesensitivity, specificity, PPV and NPV of ELISA was 99.9%, 85%, 79 % and 100% respectively.While RPR was 62%, 99 %, 100% and 63 % respectively. Percent agreement of ELISA withTPHA was 90% and corresponding kappa value was substantial 0.795. Percent agreement forRPR was 66 % with kappa value of 0.375 which was a fair agreement.Chi-square result with pvalue 0.000 which is statistical significant indicate the association between categorical variables.
Conclusion The study demonstrated that ELISA was very sensitive. There was good agreementbetween ELISA and TPHA. RPR was with high specific and weak sensitive results. There waspoor agreement between RPR and TPHA
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National Blood Bank Service