Study settings and sample size
| Level | Settings | Site name | Type of services | Sample size |
| District (urban) | Nam Dinh City | Provincial AIDS Centre | MMT + VCT | 270 |
| District (rural) | Xuan Truong District | District Health Centre | MMT + VCT + ART + GH | 151 |
| District (urban) | Tu Liem District | District Health Centre | MMT + VCT + ART + GH | 201 |
| District (urban) | Long Bien District | District Health Centre | MMT + VCT + ART + GH | 184 |
| District (urban) | Ha Dong District | Regional Polyclinic | MMT+ GH | 210 |
ART, antiretroviral therapy; GH, general healthcare; MMT, methadone maintenance treatment; VCT, voluntary counselling and testing.