Performance of serological tests for syphilis in sexually transmitted diseases clinics in Guangxi Autonomous Region, China: implications for syphilis surveillance and control.

BACKGROUND: China is experiencing a growing syphilis epidemic. Individuals are currently screened and cases are confirmed using traditional serological testing methods. METHODS: A total of 11 558 serum specimens from patients at 14 sexually transmitted diseases (STD) clinics at provincial, prefecture and county levels in Guangxi Autonomous Region were tested at local clinics using the toluidine red unheated serum test (TRUST) and the SD Bioline Syphilis 3.0 Treponema Pallidum (SD-TP) test and then transported to the National STD Reference Laboratory for TRUST and confirmatory Treponema pallidum particle assay (TPPA) testing. RESULTS: In local clinics, 13.2% of specimens were TRUST positive and 12.8% were TRUST and SD-TP positive. At the Reference Laboratory, 15.4% of specimens were TRUST positive and 11.8% were TRUST and TPPA positive. Local clinics showed a significantly higher prevalence of active syphilis compared with results from the Reference Laboratory (12.8 v. 11.8%, chi(2) = 4.59, P = 0.03). The local TRUST tests had consistent results with Reference Laboratory tests qualitatively among 96.2% of the specimens and quantitatively among 95.5% of the specimens. The algorithm of TRUST screening and then SD-TP confirmation among positive TRUST specimens at local STD clinics had 96.6% sensitivity and 99.3% specificity in diagnosing active syphilis compared with the 'gold standard' based on TRUST and TPPA positivity at the Reference Laboratory (positive predictive value 95.1% and negative predictive value 99.5%). CONCLUSION: The TRUST screening and SD-TP confirmation in combination can be used at local STD clinics for the efficient diagnosis of serologically active syphilis. However, continuing capacity building and quality assurance remain critical in ensuring the quality of syphilis diagnosis at local clinics.

The resurgence of congenital syphilis: a cocaine-related problem.

The relationship of maternal illicit drug use to congenital syphilis was studied in a population of newborn infants (N = 1012) who were screened for intrauterine exposure to illicit drugs by meconium analysis and whose mothers were screened for syphilis by the rapid plasmin reagin fluorescent treponemal antibody, absorbed (RPR/FTA-ABS) test. The result of the meconium drug screening was positive in 449 (44.3%) infants: 401 (39.6%) screening results were positive for cocaine, 71 (7%) positive for opiate, and 31 (3.1%) positive for cannabinoid. The maternal RPR/FTA-ABS result was positive in 72 (7.1%) women, and congenital syphilis was diagnosed in 46 (4.5%) infants on the basis of Centers for Disease Control and Prevention definitions. The incidence of positive RPR/FTA-ABS result (10.5% vs 4.4%) and congenital syphilis (7% vs 2.5%) was significantly higher (p < 0.01) among infants with positive results compared with those with negative drug screening results. Similarly, the incidence of positive RPR/FTA-ABS (11% vs 4.6%) and congenital syphilis (8% vs 2.3%) was significantly (p < 0.01) higher among infants with cocaine-positive results compared with those with cocaine-negative results. We conclude that maternal illicit drug use, specifically cocaine, is significantly related to the resurgence of congenital syphilis among newborn infants.

Comparison of CAPTIA syphilis G enzyme immunoassay with rapid plasma reagin test for detection of syphilis.

The CAPTIA Syphilis G enzyme-linked immunosorbent assay compared favorably with the rapid plasma reagin test when used to screen for syphilis in a low-risk population. The sensitivity and specificity of the CAPTIA Syphilis G test were 100 and 97.8%, respectively, for 646 routine specimens and 100 and 99.2%, respectively, for 265 specimens from obstetrics patients. Overall, for 911 specimens, the CAPTIA Syphilis G test showed a sensitivity of 100%, a specificity of 98.2%, and positive and negative predictive values of 78.9 and 100%, respectively. For the same population, the rapid plasma reagin test showed a sensitivity and a specificity of 96.4 and 97.5%, respectively, and positive and negative predictive values of 72 and 99.8%, respectively.

Evaluation of immunoglobulin G enzyme immunoassay for serodiagnosis of yaws.

A commercially available enzyme immunoassay (EIA), the Captia Syphilis-G immunoglobulin G (IgG) EIA, for the detection of IgG antibodies to Treponema pallidum was evaluated for use as a screening test for yaws (Treponema pallidum subsp. pertenue). The IgG EIA was compared with the fluorescent treponemal antibody absorption (FTA-ABS) test. All sera were also examined by the T. pallidum hemagglutination test and the Venereal Disease Research Laboratory test. Serum samples from 271 subjects (23 control serum samples from an area nonendemic for yaws, 58 control serum samples from an area endemic for yaws, and 190 serum samples from yaws patients and contacts) were investigated. The overall agreement between the IgG EIA and the FTA-ABS test was 90%, the sensitivity was 99%, and the specificity was 70.2%. The specificity fell as the endemicity of the disease increased: from 94.4% in the nonendemic area controls to 86.4% in the endemic area controls and to 52.3% in the yaws contacts. There was no difference in specificity between children and adults within each of the three groups. Fifteen children with clinical yaws were monitored for 9 months after treatment. The level of treponemal antibody fell consistently in 9 of the 15 children as measured by the antibody index (ratio of absorbance of the test serum to the mean absorbance of the low-titer-positive controls). Reinfection was seen in three children, with the antibody index rising with the Venereal Disease Research Laboratory test titer. The Captia Syphilis-G test is a sensitive assay for the detection of treponemal antibodies in yaws patients. However, the apparent low specificity of the test in the yaws endemic area limits its use as a screening test for yaws.