Analysis and interpretation of drug testing results from patients on chronic pain therapy: a clinical laboratory perspective

Abstract

Recent guidelines recommend monitoring for opioid and drug use in patients with chronic pain to detect use of undisclosed or illicit substances, and to determine compliance with prescribed medications. We examined the technical and clinical impact of drug testing for patients on chronic pain therapy in our clinical laboratory. Testing volumes were obtained for 4 years. Volumes from three recent months were also examined in detail to determine average turnaround time, assay performance (i.e., number of positive screening and confirmatory tests and testing discrepancies) and consistency of patient results with medication history. Our testing volume continues to grow significantly, especially in the primary care setting, with an average yearly increase of 34%. Approximately 70% of patients confirmed positive for an opioid. Other drugs were positive in <30% of patients. Twenty-nine percent of patients tested positive for a medication without a prescription. Overall, the compliance rate was 85% indicating that 15% of patients had negative test results despite being prescribed a chronic pain medication. Clinical laboratories should consider the impact of these guidelines and examine options to optimize testing such as limiting or modifying the test panel.