Table 4.
Effect of a contingency management intervention on detection of methamphetamine use by rapid urine screen and on self-reported frequency and quantity of methamphetamine use in the prior 6 weeks
| Positive methamphetamine urinalysis, n (%) | |||||
|---|---|---|---|---|---|
| Visit | Total | Contingency Management | Control | Unadjusted RR (95% CI) | Adjusted RRa (95% CI) |
| Baseline | 44/127 (35) | 28/70 (40) | 16/57 (28) | ||
| Week 6 | 27/92 (29) | 17/48 (35) | 10/44 (23) | ||
| Week 12 | 33/100 (33) | 20/55 (36) | 13/45 (29) | 1.39 (0.81, 2.38) | 1.09 (0.76, 1.57) |
| Week 18 | 39/97 (40) | 24/52 (46) | 15/45 (33) | ||
| Week 24 | 39/105 (37) | 29/58 (50) | 10/47 (21) | 1.77 (1.13, 2.78) | 1.21 (0.95, 1.54) |
| Self-reported weekly or more frequent methamphetamine use, n (%) | |||||
| Visit | Total | Contingency Management | Control | Unadjusted RR (95% CI) | Adjusted RRb (95% CI) |
| Baseline | 83/127 (65) | 51/70 (73) | 32/57 (56) | ||
| Week 6 | 32/92 (35) | 20/48 (42) | 12/44 (27) | ||
| Week 12 | 39/102 (38) | 25/56 (45) | 14/46 (30) | 1.50 (0.93, 2.42) | 1.29 (0.82, 2.04) |
| Week 18 | 37/99 (37) | 26/53 (49) | 11/46 (24) | ||
| Week 24 | 40/107 (37) | 29/60 (48) | 11/47 (23) | 2.06 (1.29, 3.29) | 1.76 (1.13, 2.73) |
| Self-reported use of more than eight quarters of methamphetamine, n (%) | |||||
| Visit | Total | Contingency Management | Control | Unadjusted RR (95% CI) | Adjusted RRc (95% CI) |
| Baseline | 59/127 (46) | 37/70 (53) | 22/57 (39) | ||
| Week 6 | 22/91 (24) | 14/47 (29) | 8/44 (18) | ||
| Week 12 | 28/99 (28) | 21/55 (37) | 7/44 (16) | 2.01 (1.09, 3.73) | 1.80 (0.95, 3.40) |
| Week 18 | 23/97 (24) | 19/52 (36) | 4/45 (9) | ||
| Week 24 | 30/105 (29) | 24/59 (40) | 6/46 (13) | 3.52 (1.70, 7.30) | 3.02 (1.47, 6.23) |
CI, confidence interval; RR, relative risk; one quarter of methamphetamine is equivalent to 0.25 grams. Statistically significant results (P < 0.05) are bolded.
aAdjusted for methamphetamine urinalysis result at baseline and stage of change for methamphetamine use at baseline (maintenance, action, preparation, contemplation, pre-contemplation, missing).
bAdjusted for baseline self-reported weekly or more frequent use of methamphetamine in the prior 6 weeks.
cAdjusted for baseline self-reported use of more than eight quarters of methamphetamine in the prior 6 weeks.