| 
      
        |  | P | OR | 95% C.I. |  
        | Lower | Upper |  
        | Sample source | detoxification center vs.    community | 0.502 | 1.41 | 0.52 | 3.88 |  
        | Gender | female vs. male | 0.001 | 8.50 | 2.51 | 28.78 |  
        | Age | ≤30 vs.    >30 | 0.717 | 0.88 | 0.44 | 1.77 |  
        | Marital status | Married vs. single | 0.892 | 1.05 | 0.50 | 2.20 |  
        | Nation | Han vs. Minority | 0.926 | 0.96 | 0.42 | 2.19 |  
        | Education | ≤9 years vs.    >9 years | 0.073 | 2.12 | 0.93 | 4.82 |  
        | Monthly income | 601-2000 vs. ≤600 | 0.994 | 1.01 | 0.32 | 3.18 |  
        | >2000 vs. ≤600 | 0.575 | 0.60 | 0.10 | 3.53 |  
        | Missing1 vs. ≤600 | 0.855 | 0.93 | 0.41 | 2.08 |  
        | IDU | yes vs. no | 0.230 | 0.33 | 0.05 | 2.02 |  
        | Commercial sex in last 12 months | yes vs. no | 0.697 | 1.20 | 0.48 | 2.98 |  
        | STD symptoms in last 12 months | yes vs. no | 0.115 | 2.30 | 0.82 | 6.50 |  |