Suboptimal Chlamydia trachomatis Detection Method Is Still Widely Used in China: Results of External Quality Assessments from 2013 to 2018

Objective: Laboratory capacity for Chlamydia trachomatis (C. trachomatis) detection is important in the diagnosis and treatment of C. trachomatis infection, appropriate clinical management of patients, and providing evidence for prevention programs. We conducted this study to assess laboratory capabilities for detecting C. trachomatis in China by analysis of external quality assessment (EQA) results from 2013 to 2018. Methods: Overall, 310/1,048 (29.58%) laboratories at national sexually transmitted disease (STD) sentinel site with 252–272 laboratories per time participated in six times of EQA. Each laboratory was requested to test the samples from EQA organization by the common method used, and the test results were reported to EQA organization for assessment. Z test and multinomial logistic regression analyses were used for data analyses. Results: Immunochromatographic test, nucleic acid amplification test (NAAT), and ELISA were used and accounted for 76.69%, 21.54%, 1.77%, respectively of all participating laboratories from 2013 to 2018. The total specificity for negative samples was 94.76%, the sensitivity for positive samples with medium and high concentration of C. trachomatis samples were 94.31% and 95.51%, respectively, but the sensitivity for sample with low concentration of C. trachomatis was 36.89%, and the immunochromatographic test had the worst sensitivity for detection of this sample (21.17% [95% CIs: 18.93%–23.60%]) among the three methods. Three factors were found to be significantly associated with the sensitivity of the low-concentration sample: the location of laboratories (East China: adjusted odds ratio [AOR]= 2.98, 95% CIs: 1.69–5.25, P < 0.05; South China: AOR= 3.34, 95% CIs: 1.38–5.48, P < 0.05; Southwest China: AOR=2.75, 95% CIs: 1.37–5.48, P<0.05, as compared with Northwest China); the types of hospitals (prevention and control agencies: AOR=0.56, 95% CIs: 0.40–0.80, P<0.05, as compared with general hospitals); and the method used (NAAT: AOR=46.99, 95% CIs: 28.49–77.48, P<0.050; ELISA: AOR=5.42, 95% CIs: 2.40–12.25, P<0.05, as compared with immunochromatographic test). Conclusion: Immunochromatographic test is widely used for C. trachomatis antigen in China; however, based on its suboptimal detection sensitivity, methods with high sensitivity such as NAAT-based point-of-care diagnostic method are recommended to apply for C. trachomatis detection, and efforts should be performed to promote the high-sensitivity methods among laboratories. Key words: Chlamydia trachomatis; ELISA; external quality assurance; immunochromatographic test; nucleic acid amplification test; sensitivity