Comparison of Auto RPR Plus and Auto TPIM Plus with Mediace RPR and Abbott Syphilis TP for Serologic Diagnosis of Syphilis

ABSTRACT

BACKGROUND: Serologic testing is considered a standard method for syphilis diagnosis. We compared Auto RPR Plus and Auto TPIM Plus with previously developed assays. METHODS: The precision around the cut-off, linearity, and recovery rate of Auto RPR Plus and Auto TPIM Plus was evaluated using their positive/negative control materials. The results of these two tests were compared with those of Mediace RPR and Abbott Syphilis TP using 431 remnant serum samples collected from people who underwent medical examinations. RESULTS: The within-run precisions (coefficient of variation, CV values) of negative/positive control materials of Auto RPR Plus, Mediace RPR, Auto TPIM Plus and Abbott Syphilis TP were 15.7/2.3%, 20.4/2.3%, -/2.7%, and 8.5/2.3%, respectively; between-run precisions were 67.7/3.3%, 39.1/3.4%, -/4.0%, and 7.0/1.5%, respectively. Auto RPR Plus showed better precision around the cutoff level (1.0 U) compared to Mediace RPR (7.2–7.3% vs. 12.2–14.3%). The CVs of Auto TPIM Plus around the cutoff (10.0 U) were 13.5% at 10.5 U and 6.6% at 12.5 U. Agreement rates between Auto RPR Plus and Mediace RPR and between Auto TPIM Plus and Abbott Syphilis TP were 97.2% and 98.4%, respectively. However, twelve samples showed discrepant results for Auto RPR Plus (−)/Mediace RPR (+) and false-positive Mediace RPR results could not be excluded around the cutoff of 1.0 U. CONCLUSIONS: Auto RPR Plus showing good precision near the cutoff can be used for syphilis screening in health checkups. However, Auto TPIM Plus needs improvement in precision and adjusting the cutoff to be used for syphilis screening.