UNASSIGNED: Rapid plasma reagin (RPR) and Treponema pallidum (TP) antibody test kits are often used to diagnose syphilis, although the relationship between their measured values is unclear. We aimed to reveal the relevance of these kits\' results.
UNASSIGNED: In all, 143 sera from 110 patients were tested using 12 TP kits and 5 RPR kits and the results compared.
UNASSIGNED: The specificity and sensitivity of RPR kits were 81-96% and 95-100%, respectively. The correlation coefficients (0.849-0.934) considerably differed between the manual RPR card test and latex agglutination (LA) assay kits. The following sensitivities were obtained: 82-91% for TP fluorescent treponemal antibody absorption assay (FTA-ABS), TP hemagglutination assay (HA), and TP particle agglutination assay (PA); 94-95% for TP LAs; and 92-100% for chemiluminescent immunoassay (CLIA), chemiluminescent enzyme immunoassay (CLEIA), and immunochromatography assay (IC). Correlation coefficients between TP kits were 0.753-0.974, and the measured values varied. Changes in RPR and quantifiable TP kits were the same for patients with reinfected syphilis and with syphilis under treatment.
UNASSIGNED: RPR tests had lower specificity than TP antibody tests. RPR card test and RPR LAs had similar specificity and sensitivity, but their measured values were different. RPR should be measured using automatic RPR LA without setting the upper limit of the reported value. RPR LA should also be standardized. The sensitivity of TP antibody was better in CLIA, CLEIA, and IC than in FTA-ABS, HA, PA, and LA. Therefore, TP antibody kits should be standardized and quantified.

UNASSIGNED: Automated analyzer-based nontreponemal serological tests for syphilis (STS) have been used for several decades.
UNASSIGNED: In this study, we evaluated serological responses to treatment and proposed clinical guidelines for automated STS.
UNASSIGNED: This retrospective cohort study analyzed human immunodeficiency virus-negative syphilis patients who were diagnosed with automated rapid plasma reagin (auto RPR) tests as a nontreponemal STS, and who also received the fluorescent treponemal antibody-absorption test as a confirmatory test. The ratio of auto RPR values after treatment against those at baseline was defined as the auto RPR ratio for the analysis of the serological response to treatment. The cutoff value for reliable seroreversion prediction was assessed with receiver-operating-characteristic curves.
UNASSIGNED: Overall, 89.7% of participants (78/87) seroreverted and 10.3% of participants (9/87) remained serofast during the two-year follow-up period. We were unable to describe trends in the changes among auto RPR values within six months after treatment because of high variation. All of the patients who had an auto RPR ratio ≥1.0 after six months continuously had positive serologic results during their 24-month follow-up and were classified as a serofast group. The receiver-operating-characteristic curves revealed a 25% reduction in auto RPR values nine months after treatment and predicted seroreversion with a sensitivity of 96.2% and a specificity of 100%.
UNASSIGNED: The most important primary checkpoint for syphilis treatment response is an increase in automated nontreponemal STS six months after treatment. Thus, we recommend monitoring the treatment response with an auto RPR.

To characterize the CBFP reaction in the modern era, we analyzed the results of parallel rapid plasma reagin (RPR) and Treponema pallidum particle agglutination (TPPA) tests from a total of 63,765 blood samples obtained at Zhongshan Hospital in the Medical College of Xiamen University from May 2008 to February 2013. Among the 63,765 tested blood samples, 206 (0.32%) had the CBFP reaction. In multivariate analysis, an increased likelihood of the CBFP reaction was associated with female subjects, subjects ≥80years old, and subjects between 16 and 35years old (P<0.05). The CBFP reaction occurred in association with 17 categories of disease, including 60 types of diseases, in the 206 subjects. To our knowledge, a number of these diseases had not been previously reported to be associated with the CBFP in the RPR test, including false labor, megaloblastic anemias, aplastic anemias, redundant prepuce, congenital malformation of heart, and salpingitis. Among the 206 patients with the CBFP reaction, 35 patients were subjected to follow-up for five years. 26 out of 35 these patients were at a 1:1 initial RPR titer, 8 out of 35 patients were at a 1:2 initial RPR titer, and 1 out of 35 patients were at a 1:4 initial RPR titer. 30 subjects had their RPR seroreverted. In our opinion, additional CBFP research using a large sample population will contribute to the identification of additional underlying serious disorders that are not related to syphilis. Such results could be useful for the prediction and diagnosis of these diseases.

BACKGROUND: Algorithms for the diagnosis of syphilis continue to be a source of great controversy, and numerous test interpretations have perplexed many clinicians.
METHODS: We conducted a cross-sectional study of 24 124 subjects to analyze 3 syphilis testing algorithms: traditional algorithm, reverse algorithm, and the European Centre for Disease Prevention and Control (ECDC) algorithm. Every serum sample was simultaneously evaluated using the rapid plasma reagin, Treponema pallidum particle agglutination, and chemiluminescence immunoassay tests. With the results of clinical diagnoses of syphilis as a gold standard, we evaluated the diagnostic accuracy of the 3 syphilis testing algorithms. The κ coefficient was used to compare the concordance between the reverse algorithm and the ECDC algorithm.
RESULTS: Overall, 2749 patients in our cohort were diagnosed with syphilis. The traditional algorithm had the highest negative likelihood ratio (0.24), a missed diagnosis rate of 24.2%, and only 75.81% sensitivity. However, both the reverse and ECDC algorithms had higher diagnostic efficacy than the traditional algorithm. Their sensitivity, specificity, and accuracy were 99.38%-99.85%, 99.98%-100.00%, and 99.93%-99.96%, respectively. Moreover, the overall percentage of agreement and κ value between the reverse and the ECDC algorithms were 99.9% and 0.996, respectively.
CONCLUSIONS: Our research supported use of the ECDC algorithm, in which syphilis screening begins with a treponemal immunoassay that is followed by a second, different treponemal assay as a confirmatory test in high-prevalence populations. In addition, our results indicated that nontreponemal assay is unnecessary for syphilis diagnosis but can be recommended for determining serological activity and the effect of syphilis treatment.