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Kim, Lee, Lee, Kim, Kwon, Min, Seo, and Kim: Comparison of Quantitative Results among Two Automated Rapid Plasma Reagin (RPR) Assays and a Manual RPR Test
Original Article

Korean J Leg Med 2009;29(4):331-337.

Published online: 14 January 2009

DOI: https://doi.org/10.3343/kjlm.2009.29.4.331

Comparison of Quantitative Results among Two Automated Rapid Plasma Reagin (RPR) Assays and a Manual RPR Test

Yeong Sic Kim, M.D.1, Jehoon Lee, M.D.1, Hae Kyung Lee, M.D.1, Hyunjung Kim, M.D.1, Hi Jeong Kwon, M.D.1, Ki Ouk Min, M.D.2, Eun Joo Seo, M.D.2, Soo-Young Kim, M.D.1

1Departments of Laboratory Medicine and Pathology, Seoul, Korea

2College of Medicine, The Catholic University of Korea, Seoul, Korea

Corresponding author: Soo-Young Kim, M.D. Department of Laboratory Medicine, The Catholic University of Korea, St. Vincent's Hospital, 93-6 Ji-dong, Paldal-gu, Suwon 442-723, Korea Tel: +82-31-249-7594, Fax: +82-31-244-6786 E-mail: vsykim@catholic.ac.kr

      Revised 15 February 200922 July 2009       Accepted 8 July 2009

Copyright © 2009 Korean Society for Legal Medicine

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background:

We compared two automated Rapid Plasma Reagin (RPR) assay kits with a manual RPR assay kit to evaluate the possibility of using the two automated RPR assays as an alternative to the manual RPR assay for a quantitative monitoring.

Methods:

One hundred eighty-five samples were analyzed, including 16 sera from patients with primary, secondary, and latent syphilis. Measured RPR unit (R.U.) values of two automated RPR assay kits, Mediace RPR (Sekisui Chemical Co., Ltd, Japan) and HBi Auto RPR (HBI Co., Ltd, Korea), were compared with the RPR titers of Macro-Vue RPR card test (Becton Dickinson BD Microbiology systems, USA). As a confirmatory test, Anti-Treponema pallidum EUROLINE WB (IgG) and Anti-Treponema pallidum EUROLINE WB (IgM) (Euroimmun, Germany) were used.

Results:

There was a prozone effect with Mediace RPR at RPR titer (card test) of 1:16, but not with HBi Auto RPR. The R.U. values of the two automated RPR assays did not show proportional increase to the RPR titer. Agreement between manual RPR and two automated RPR assay kits, Mediace RPR assay and HBi Auto RPR assay, were 83.8% and 83.2%, respectively.

Conclusions:

The two automated RPR assay kits could not be used as an alternative to manual RPR test for quantitative analysis of RPR titer. As Mediace RPR shows a prozone effect at relatively low RPR titer, caution is needed in the interpretation of the measured values.

Keywords: Rapid Plasma Reagin, RPR titer, Prozone effect

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Fig. 1.
Measurement of reagin antibody using two automated RPR assay kits, Mediace RPR and HBi Auto RPR. Serial two-fold diluted samples were tested and the RPR titers (RPR card test) of the undiluted samples were 1:64 (A), 1:32 (B), 1:16 (C and D), 1:8 (E), and 1:2 (F).
kjlm-29-331f1.tif
Table 1.
Subject characteristics
  No. Sex, M/F Age, mean (SD)
Syphilis      
Primary 3 2/1 33 (10)
Secondary 4 3/1 42 (11)
Latent 9 7/2 44 (15)
Past treated syphilis 37 24/6 60 (12)
Pregnant women 27 0/27 32 (5)
Rheumatic diseases 35 5/30 51 (17)
Infection 20 11/9 60 (17)
Other diseases 50 21/29 57 (23)
Total 185 74/111 51 (19)
Table 2.
The number of samples with positive results (%) according to the assay kits
  No. WB (IgM)∗ WB (IgG)† TPHA VDRL RPR card Mediace RPR HBi Auto RPR
Syphilis                
Primary 3 3 (100) 3 (100) 3 (100) 3 (100) 3 (100) 3 (100) 3 (100)
Secondary 4 4 (100) 4 (100) 4 (100) 4 (100) 4 (100) 4 (100) 4 (100)
Latent 9 1 (11.1) 9 (100) 9 (100) 9 (100) 9 (100) 5 (55.6) 5 (55.6)
Past treated syphilis 37 0 (0) 37 (100) 36 (97.3) 30 (81.8) 28 (75.7) 6 (16.2) 7 (18.9)
No history of syphilis 132 0 (0) 0 (0) 1 (0.8) 14 (10.6) 9 (6.8) 5 (3.8) 6 (4.5)
Total 185 8 (4.3) 53 (28.7) 53 (28.7) 60 (32.4) 53 (28.7) 23 (12.4) 25 (13.5)

∗ Western blot (IgM), Anti-Treponema pallidum EUROLINE WB (IgM) (Euroimmun);

† Western blot (IgG), Anti-Treponema pallidum EUROLINE WB (IgG) (Euroimmun).

Abbreviations: WB, Western Blot; TPHA, Treponema Pallidum hemagglutination assay; VDRL, Venereal Disease Research Laboratory; RPR, Rapid Plasma Reagin

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