Clinical analysis and methodological evaluation of syphilis infection in patients in a first-class tertiary hospital in Suzhou, China.

Objective: To explore the distribution and epidemiological characteristics of patients with syphilis in a first-class tertiary hospital and to evaluate the coincidence rate between chemiluminescence immunoassay (CLIA) and Treponema pallidum particle agglutination assay (TPPA).

Methods: The medical records of 247,501 outpatients and inpatients were retrospectively analyzed. TPPA was used to verify positive and suspected cases, and the coincidence rate between CLIA and TPPA was evaluated. Receiver operating characteristic (ROC) curve was used to determine optimal diagnostic thresholds.

Results: Of the 247,501 serum samples, 5,173 were detected positive for syphilis using CLIA, with a detection rate of 2.09% and a men-to-women ratio of 1.39. The chi-square test showed that sex and age were both factors that affected the detection rate (χ²=229.51, P < 0.0001). In addition, urology, orthopedics, cardiology, general surgery, gastroenterology, and gynecology represented the top six departments with the highest numbers of positive cases. Comparative analysis showed that the overall coincidence rate between CLIA and TPPA was 80.24%. Analysis of the ROC curve showed that the area under the curve (AUC) was 0.936 (95% confidence interval [CI]: 0.929-0.942, P < 0.0001) using sample/cut-off value (S/CO) as a diagnostic indicator. The results showed that an S/CO value of 3.945 was the best diagnostic value for the CLIA method, with a diagnostic specificity of 93.64% and a sensitivity of 81.90%.

Conclusions: Syphilis is widely distributed in various hospital departments and primarily affects middle-aged and older individuals. For cases that have been initially screened as positive or suspicious, TPPA and other tests should be used for verification to avoid misdiagnosis and missed diagnosis.