Quantitative testing of buprenorphine and norbuprenorphine to identify urine sample spiking during office-based opioid treatment

Background: Patients may spike urine samples with buprenorphine during office-based opioid treatment to simulate adherence to prescribed buprenorphine, potentially to conceal diversion of medications. However, routine immunoassay screens do not detect instances of spiking, as these would simply result in a positive result. The aim of this study was to report on the experience of using quantitative urine testing for buprenorphine and norbuprenorphine to facilitate the identification of urine spiking. Methods: This is a retrospective chart review of 168 consecutive patients enrolled in outpatient buprenorphine treatment at an urban academic medical setting between May 2013 and August 2014. All urine samples submitted were subjected to quantitative urine toxicology testing for buprenorphine and norbuprenorphine. Norbuprenorphine-to-buprenorphine ratio of less than 0.02 were further examined for possible spiking. Demographic and clinical variables were also extracted from medical records. Clinical and demographic variables of those who did and did not spike their urines were compared. Statistically significant variables from the univariate testing were entered as predictors of spiking in a regression analysis. Results: A total of 168 patients were included, submitting a total of 2275 urine samples. Patients provided on average 13.6 (SD = 9.9) samples, and were in treatment for an average 153.1days (SD = 142.2). In total, 8 samples (0.35%) from 8 patients (4.8%) were deemed to be spiked. All of the samples suspected of spiking contained buprenorphine levels greater than 2000ng/mL, with a mean norbuprenorphine level of 11.9ng/mL. Spiked samples were submitted by 6 patients (75.0%) during the intensive outpatient (IOP) phase of treatment, 2 patients (25.0%) during the weekly phase, and none from the monthly phase. Regression analysis indicated that history of intravenous drug use and submission of cocaine-positive urine samples at baseline were significant predictors of urine spiking. Conclusions: Even though only a small number of patients were identified to have spiked their urine samples, quantitative testing may help identify urine spiking during office-based opioid treatment with buprenorphine.