Table 1 Demographic characteristics of the study population
| Individuals | 161 |
| Total test results | 2588 |
| Age at initial visit | 38 (SD 11, Median 35) |
| Gender at initial visit | M = 77(47.8%) F = 79(49%) Unknown 5 (3%) |
| Tests per patient | Average 16.1 (SD 11.1, Median 15) Range per patient 1–48 |
| Days Followed | 289.6 (SD 218.5 Median 255) Range 0–660 days |
| Patients with buprenorphine and no unexpected substances in the urine | 104 Patients (64.4%) (N = 161) |