An Evaluation of the Clinical Tools Used to Monitor Illicit Methamphetamine Use Among Chronic Pain Patients: A Cross Sectional Retrospective Study.

Purpose: Illicit drug use continues to be a concern for adults on opioid therapy for chronic pain. Prescribers use tools such as urine screening and confirmatory testing with mass spectrometry to monitor adherence to chronic opioid therapy contracts. Design: A cross sectional retrospective study was conducted using electronic medical records. Methods: Data was analyzed from 6558 urine samples of adult outpatients receiving opioid therapy at an urban pain specialty clinic who consented to urine drug tests. Results: From October 18, 2021, to October 21, 2022, 569 were positive amphetamine with immunoassay testing. 310 (54%) of those samples were absent amphetamine with or without methamphetamine while 259 (45.5%) were true positive amphetamine proven by confirmation testing. Analysis of confirmatory testing results identified 281 samples positive for amphetamine with or without methamphetamine. 71 samples confirmed positive for methamphetamine with or without amphetamine. 37 (52.1%) of those methamphetamine samples screened positive for amphetamine and 34 (47.9%) samples screened negative for amphetamine. 48 of the methamphetamine samples were sent for chiral confirmation testing. 45 (93.8%) samples were positive for D-methamphetamine while 3 (6.2%) samples were positive for L-methamphetamine. Only 5 (11.1%) of the 45 patients whose samples were positive for d- methamphetamine reported the use of illicit drugs before their urine sample was tested. Discussion: Confirmatory testing with mass spectrometry can detect illicit drugs, such as methamphetamine, with high sensitivity and specificity and should be used with all samples given the low sensitivity of screening immunoassay. It is of utmost importance that opioid pain medicine prescribers know the many possible interpretations of these results so that they are equipped to make appropriate clinical decisions to ensure the safety of the patient, prescriber, and practice.