[Evaluation of performance and false positivity of Mediace RPR test that uses a chemistry autoanalyzer].
BACKGROUND
We evaluated the performance and false positive rate of Mediace RPR test (Sekisui, Japan), a newly introduced nontreponemal test using a chemistry autoanalyzer.


METHODS
The sensitivity of Mediace RPR test was analyzed using sera from 50 patients with syphilis in different stages (8 primary, 7 secondary, and 35 latent), 14 sera positive with fluorescent treponemal antibody absorption (FTA-ABS) IgM, and 74 sera positive with conventional rapid plasma regain (RPR) card test (Asan, Korea) and also positive with Treponema pallidum hemagglutination (TPHA) test or FTA-ABS IgG test. The specificity was analyzed on 108 healthy blood donors. We also performed RPR card test on 302 sera that had been tested positive with Mediace RPR test and also performed TPHA or FTA-ABS IgG test to analyze the false positive rate of Mediace RPR test. A cutoff value of 0.5 R.U. (RPR unit) was used for Mediace RPR test.


RESULTS
Mediace RPR test on syphilitic sera of different stages (primary, secondary, and latent stages) and FTA-ABS IgM positive sera showed a sensitivity of 100%, 100%, 82.9% and 100%, respectively. Among the 74 sera positive with conventional RPR card test and TPHA or FTA-ABS IgG test, 55 were positive with Mediace test. The specificity of Mediace RPR test on blood donors was 97.2%. Among the 302 sera positive with Mediace RPR test, 137 sera (45.4%) were negative by RPR card and TPHA/FTA-ABS IgG tests.


CONCLUSIONS
Although the sensitivities of Mediace RPR were good for primary and secondary syphilis, due to its high negative rate of Mediace RPR over the conventional RPR positive samples, further studies are necessary whether it can replace conventional nontreponemal test for screening purpose. Moreover, in view of the high false positive rate, positive results by Mediace RPR test should be confirmed with treponemal tests.
Noh
Jaekwang
J
Department of Laboratory Medicine, Konkuk University College of Medicine, Seoul, Korea.
Ko
Hak Hyun
HH
Yun
Yeomin
Y
Choi
Young Sook
YS
Lee
Sang Gon
SG
Shin
Sue
S
Han
Kyou Sup
KS
Song
Eun Young
EY
D001322:Autoanalysis / Q000379:methods; D005189:False Positive Reactions; D006801:Humans; D012372:ROC Curve; D012680:Sensitivity and Specificity; D013587:Syphilis / Q000175:diagnosis*; D013588:Syphilis Serodiagnosis / Q000379:methods*