Combining Urine Tests with Self-Report May Be More Accurate for Measuring Cannabis Abstinence
- Cannabis use prevalence in the United States more than doubled, from 4.1% to 9.5%, between 2001/2 and 2012-13. In addition, approximately 12% of individuals who have used cannabis in the past year meet criteria for cannabis use disorder.
- However, measures of changes in cannabis use patterns over time are difficult to validate.
Detection of cannabinoids in urine is subject to both physiological and pharmacological influences, including individual metabolism, hydration, frequency, concentration, and quantity of cannabis used. Frequent cannabis users may submit positive urine samples for extended periods of time beyond initial abstinence, a particularly challenging issue in cannabis cessation clinical trials.
Using a combination of self-reported cannabis abstinence with urine testing for cannabinoids concentrations in a clinical trials setting may improve accuracy, but this has not been well characterized.
In an effort to remedy that, this study assessed the agreement between various cannabinoid cutoffs and self-reported abstinence across three clinical trials, one including contingency management for abstinence (CTN-0053).
All three trials included both participant self-report and weekly urine samples for cannabis and creatinine concentration measurements. Four hundred and seventy-three participants with 3787 valid urine specimens were included. Data were assessed for agreement between self-reported 7+day abstinence and urine cannabinoid tests, using biological cutoffs of 50, 100, and 200ng/mL of THCCOOH (metabolized THC excreted in urine). Changes in creatinine-normalized THCCOOH (25%/50% decrease) were also evaluated.
Results found that:
agreement between measured THCCOOH and self-reported abstinence increases with increasing cutoff concentrations, while the agreement with self-reported non-abstinence decreases with increasing cutoff concentrations;
combining THCCOOH cutoffs with recent changes in creatinine-normalized THCCOOH provided a better agreement in those self-reporting abstinence;
inclusion of contingency management decreased the agreement between biological measurements and self-reported abstinence.
Conclusions: Using combinations of biological measurements and self-reported abstinence, confirmation of study-related abstinence may be verifiable earlier and with greater accuracy than relying on a single measurement.
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