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%).


CONCLUSIONS
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.
Yin
Yue-Ping
YP
China CDC National Center for STD Control, Chinese Academy of Medical Sciences and Peking Union Medical College Institute of Dermatology, 12 Jiangwangmiao Street, Nanjing 210042, China.
Wei
Wan-Hui
WH
Wang
Hong-Chun
HC
Zhu
Bang-Yong
BY
Yu
Yan-Hua
YH
Chen
Xiang-Sheng
XS
Peeling
Rosanna W
RW
Cohen
Myron S
MS
D000293:Adolescent; D000328:Adult; D000554:Ambulatory Care Facilities / Q000458:organization & administration; D002681:China / Q000453:epidemiology; D005260:Female; D016508:Fluorescent Treponemal Antibody-Absorption Test / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D011159:Population Surveillance / Q000379:methods*; D015995:Prevalence; D011933:Reagent Kits, Diagnostic; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012959:Socioeconomic Factors; D013587:Syphilis / Q000175:diagnosis* / Q000453:epidemiology*; D014209:Treponema Immobilization Test / Q000706:statistics & numerical data*; D055815:Young Adult
D011933:Reagent Kits, Diagnostic