Table 2.

Model validation with urine collected from 67 outpatient cannabis smokers initiating cannabis abstinence. Specimen 1 groups are based on urinary creatinine-normalized (CN)-11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THCCOOH) concentrations. Data are %reuse predictions exceeding the upper prediction limits (80, 90, 95 and 99% probabilities) and therefore, are suggestive of new cannabis use. Expected %re-use prediction rates are 10, 5, 2.5 and 0.5%, respectively. Abstinence was closely monitored with daily observed urine specimens, A includes all data; B includes all data after application of Rules 1 and 2 (see text).

Specimen 1 CN-THCCOOH concentration (ng/mg)	A				B
	80%	90%	95%	99%	80%	90%	95%	99%
6–14.9	13.7	11.7	7.8	2.9	6.9	5.3	3.7	1.6
15–24.9	4.7	2.9	2.2	1.0	4.7	2.9	2.2	1.0
25–49.9	2.4	1.0	0.6	0.3	2.4	0.6	0.4	0.1
50–99.9	1.5	1.0	0.6	0.2	1.3	0.8	0.5	0.2
100–199.9	6.7	4.2	2.9	1.8	2.6	0.9	0.3	0.1
200–399.9	30.9	25.6	19.4	12.4	2.3	1.0	0.3	0.3
400–599.9	26.3	21.5	19.7	15.4	8.6	4.9	3.7	2.2
600–1166	36.1	32.7	29.5	24.3	5.4	3.8	3.3	1.1