Abstract: 【Abstract】 Objective To evaluate the early infection status among reported cases of latent syphilis, and to investigate factors related to early latent syphilis. Methods A cross-sectional study was conducted among patients with newly diagnosed latent syphilis in 6 medical institutions in Nanning city from April to August in 2022. The demographic and sexual behavioral characteristics, medical history, and laboratory test results of the patients were retrospectively analyzed to screen out those with early latent syphilis. The logistic regression model was used to analyze the factors related to early latent syphilis, and the receiver operating characteristic （ROC） curve to evaluate their diagnostic value. Results A total of 147 patients with latent syphilis were included, of whom 94 were males and 53 were females, and their ages ranged from 18 to 88 years; 89 （60.5%） were diagnosed with early latent syphilis. The patients were significantly younger in the early latent syphilis group （32.43 ± 13.61 years） than in the late latent syphilis group （50.45 ± 15.80 years, P < 0.001）. There were significant differences in the marital status and logarithmic values of serum toluidine red unheated serum test （TRUST） titers between the early latent syphilis group and late latent syphilis group （both P < 0.001）, while there were no significant differences in the gender ratio, number of non-marital sexual partners, or proportions of patients with a positive history of diagnosis and treatment of syphilis in spouses or sexual partners between the above two groups （all P > 0.05）. The logistic regression analysis showed that the age （OR = 0.922, 95% CI: 0.877 - 0.969, P = 0.001） and serum TRUST titers （OR = 1.900, 95% CI: 1.427 - 2.530, P < 0.001） were associated with the diagnosis of early latent syphilis. The areas under the ROC curves of the age and serum TRUST titers in predicting early latent syphilis were 0.811 and 0.825 respectively, and their adjusted optimal cut-off values were 36 years and 1∶8 respectively. Conclusion Early latent syphilis predominated in the reported cases of latent syphilis, and the age of ≤ 36 years and the serum TRUST titer of ≥ 1∶8 may indicate the diagnosis of early latent syphilis.

Key words: Syphilis, latent, Syphilis serodiagnosis, Age factors, Early latent syphilis