Association between syphilis seroprevalence and age among blood donors in Southern China: an observational study from 2014 to 2017

Wu, Xiaobing; Guan, Yang; Ye, Jianbin; Fu, Hanlin; Zhang, Chunlai; Lan, Lina; Wu, Fengxin; Tang, Fen; Wang, Feng; Cai, Yumao; Yu, Weiye; Feng, Tiejian

historical infection and active infection. Historical infection was defined as TPPA positive but TRUST negative, and active infection as both TPPA and TRUST positive. 15 The overall syphilis infection was defined as TPPA positive, including both historical and active infection. Moreover, high-titre was defined as active infection patients with a quantitative titre of ≥ 1∶8. infection among all blood donors in different age groups. There were four age groups, <25 years, 25-34 years, 35-44 years, and ≥45 years, fully considering the age coverage of blood donors and age classification in previous studies. 16 , 17 We calculated the crude prevalence and its 95% confidence interval (CI). The chi-squared (χ 2 ) test for trend was used to assess the prevalence difference among age groups. Line graphs were used to describe the change in prevalence for both syphilis infection and active infection among the age groups after stratification of gender and year of donation. Odds ratios (ORs) and their 95% CIs were calculated when comparing the risk of syphilis infection and active infection between the ≥ 45 years age group and other age groups. Furthermore, we described the distribution of TRUST titres among age groups and compared the difference using the χ 2 test. Data were analysed using SPSS 17.0 for Windows; p < 0.05 was considered statistically significant in the χ 2 test.