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.

Menza et al. BMC Public Health 2010 10:774   doi:10.1186/1471-2458-10-774

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