Chronic opioid therapy urine drug testing in primary care: prevalence and predictors of aberrant results.

BACKGROUND: Urine drug tests (UDTs) are recommended for patients on chronic opioid therapy (COT). Knowledge of the risk factors for aberrant UDT results could help optimize their use. OBJECTIVE: To identify primary care COT patient and opioid regimen characteristics associated with aberrant UDT results. DESIGN: Population-based observational. SAMPLE: 5,420 UDTs for Group Health integrated group practice COT patients. MEASURES: Group Health database measures of patient demographics, medical history, COT characteristics, and UDT results. RESULTS: Thirty percent of UDTs had aberrant results, including prescribed opioid non-detection (12.3%), tetrahydrocannabinol (THC; 11.2%), non-prescribed opioid (5.3%), illicit drug (excluding THC; 0.6%), non-prescribed benzodiazepine (1.7%), and dilute (4.8%). Adjusted odds ratios (95% CI) of any aberrant result were higher for males than females (1.24 [1.07, 1.43]), patients with versus without prior substance use disorder diagnoses (1.42 [1.17, 1.72]), and current smokers versus non-smokers (1.50 [1.30, 1.73]). Odds ratios were lower for patients aged 45-64 (0.77 [0.65, 0.92]) and 65+ (0.40 [0.32, 0.50]) versus patients aged 20-44 and for patients on long-acting opioids only (0.72 [0.55, 0.95]) or long-acting plus short-acting (0.67 [0.54, 0.83]) versus short-acting only. Adjusted odds of prescribed opioid non-detection were lower for patients aged 45-64 (0.79 [0.63, 0.998]) and 65+ (0.44 [0.32, 0.59]) versus patients aged 20-44, for those on 40-<120 mg daily morphine-equivalent dose (0.52 [0.39, 0.70]) or 120+ mg (0.22 [0.11, 0.43]) versus <40 mg, and for patients on long-acting (0.35 [0.21, 0.57]) or long-acting plus short-acting (0.35 [0.24, 0.50]) opioids (versus short-acting only); and odds ratios were higher for patients with versus without prior diagnoses of substance use disorder (1.70 [1.31, 2.20]). CONCLUSIONS: In this primary care setting, results were aberrant for 30% of UDTs of COT patients, largely because of prescribed opioid non-detection and THC. Aberrant results of almost all types were more likely among patients under the age of 45. Other risk factors varied across aberrancies, but commonly included current smoking and prior substance use disorder diagnosis.