The increasing prevalence of serologic markers for syphilis among Chinese blood donors in 2008 through 2010 during a syphilis epidemic

Background: In China, the growing syphilis epidemic parallels the spread of human immunodeficiency virus (HIV) in the general population. This study evaluated the prevalence and incidence of serologic markers for syphilis among donors at five Chinese blood centers. Study Design and Methods: We examined whole blood and apheresis donations collected from January 2008 through December 2010. Postdonation testing of syphilis was conducted using two different Treponema pallidum antibody enzyme-linked immunosorbent assay kits. The prevalence of serologic markers for syphilis (%), and the rate of coinfection with HIV-1/2, hepatitis B virus (HBV), and hepatitis C virus (HCV) were calculated. A multivariable logistic regression analysis was conducted examining donor characteristics associated with positive syphilis serology. Seroconversion rate and syphilis incidence were estimated. Results: Of 801,511 donations, 60% were from first-time donors and 40% were from repeat donors. There was a significant increase in syphilis serologic markers among first-time donors with 0.41, 0.45, and 0.57% positivity over 3 years (p < 0.001). Approximately 2.8, 0.8, and 0.5% of HIV-1/2-, HBV-, and HCV-positive donations also tested reactive for syphilis. Logistic regression results suggest that first-time donors were nine times more likely to be syphilis positive than repeat donors. Higher syphilis positivity was associated with donors older than 25 years and with less education. Estimated incidence among repeat donations was 33 (95% confidence interval, 29-39) per 100,000 person-years. Conclusion: The increase in syphilis serologic prevalence reflected the syphilis epidemic in the general population. Without screening, most of these syphilis-positive donations would get into the blood supply. Thus, during a syphilis epidemic, continued syphilis screening of blood donations may be important to maintain blood safety and public health.