We are happy to announce that The Journal of Basic and Clinical Health Sciences (JBACHS) is indexed by the Emerging Sources Citation Index since November 2017.
Journal of Basic and Clinical Health Sciences 2018 , Vol 2 , Issue 1
Determination of a Sample-to-Cutoff Ratio to Predict True-Positivity in Blood Donor Samples Screened for Syphilis by a Chemiluminescent Immunoassay
İ. Ebru Akçakanat1,Özgen Alpay Ozbek1,Yavuz Doğan1,Yusuf Hakan Abacıoğlu2
1Dokuz Eylul University Medical Faculty, Medical Microbiology, İzmir, Turkey
2İzmir University of Economics, Faculty of Medicine, Basic Medical Sciences, İzmir, Turkey
DOI : 10.30621/jbachs.2018.277 Purpose: The use of Architect Syphilis TP (CMIA) in the blood bank raised the number of syphilis positive samples requiring confirmation. The aim of this study is to determine a sample-to-cutoff (s/co) ratio for CMIA predicting ≥95% of true-positive samples to reduce these samples.

Methods: CMIA reactive samples (n=177) were evaluated by Western blot (WB) as the reference standard, as well as by Treponema pallidum hemagglutination (TPHA) and Rapid Plasma Reagin (RPR) tests. The s/co ratio predicting ≥95% of true-positive samples was defined as the threshold leaving ≥95% of WB confirmed samples greater than the particular value. The performances of TPHA and RPR tests were also evaluated with respect to s/co ratios of CMIA positive samples.

Results: The s/co ratio 15.17 predicted a true-positive result for ≥95% of samples tested (95% confidence interval: 85.9–99.3) and reduced the number of samples requiring confirmation by 29.9%. Higher s/co ratios were correlated with the increasing number of bands on WB strips (p<0.0001, R=0.906). For the samples with s/co ratios between 3 and 15.17, the agreement of TPHA and WB test results were 90%. The lowest s/co ratio where TPHA was positive, was 3.1. Although RPR predicted >95% of positive samples with s/co ratios ≥15, its sensitivity was 47.7%.

Conclusion: Higher s/co ratios can be used to define true-positivity and may indicate an active infection. TPHA may replace WB to confirm samples with s/co ratios between 3 and 15. RPR should not be used as a screening test in blood banks as it could miss almost half of the truepositive samples. Keywords : Syphilis; architect syphilis; transfusion-transmitted disease; reverse sequence