P OR 95% C.I. Lower Upper Sample source detoxification center vs. community 0.095 0.09 0.01 1.53 Gender female vs. male 0.019 7.44 1.40 39.57 Age ≤30 vs. >30 0.131 2.19 0.79 6.02 Marital status Married vs. single 0.038 2.51 1.05 6.00 Education ≤9 years vs. >9 years 0.030 3.06 1.12 8.39 IDU yes vs. no 0.323 1.73 0.58 5.10 STD symptoms in last 12 months yes vs. no 0.601 0.61 0.10 3.91

Table 4: Logistic regression analysis of sample characteristics associated with syphilis in Xinjiang Kashi (syphilis prevalence 10.4%)