Agreement of Enzyme-Linked Immunosorbent Assay With Rapid Plasma Reagin and Treponema pallidum Hemagglutination Assay for Screening and Diagnosis of Syphilis at National Blood Bank Service in Addis Ababa, Ethiopia

Abstract

Objectives To determine the agreement of enzyme-linked immunosorbent assay (ELISA) with rapid plasma reagin (RPR) and Treponema pallidum hemagglutination assay (TPHA) at the National Blood Bank Service in Addis Ababa, Ethiopia. Methods The study was conducted from January to June 2016 on 190 syphilis ELISA positive and 190 negative samples stored at the National Blood Bank Service (NBBS) laboratory, Addis Ababa, Ethiopia, from July 2015 to December 2015. A systematic random sampling method was used to select samples. The data were analyzed by SPSS version 20 software. The overall percent agreement, kappa value, sensitivity, specificity, positive predictive value, and negative predictive value of the tests were calculated. Results From 190 positive sera, 151 (80%) were confirmed as positive by TPHA, and 39 (20%) were found false positive; 59 (31.1%) of them were positive and 131 (68.9%) were false positive by RPR. From 190 negative sera, all were negative by RPR and TPHA. The sensitivity, specificity, positive predictive value, and negative predictive value of TPHA were 99.9%, 85%, 79%, and 100%, respectively, while RPR was 62%, 99%, 100%, and 63%, respectively. Overall percent agreement of ELISA with TPHA was 90% and corresponding kappa value was 0.795, and ELISA with RPR was 66% with a kappa value of 0.375. Conclusion TPHA was very sensitive; there was substantial agreement with ELISA. Whereas RPR was highly specific and less sensitive, there was fair agreement with ELISA. TPHA can be used interchangeably with ELISA to screen blood in blood bank laboratories.