Comparative evaluation of the accuracy of immunoassay with liquid chromatography tandem mass spectrometry (LC/MS/MS) of urine drug testing (UDT) opioids and illicit drugs in chronic pain patients.

BACKGROUND: The challenge for physicians in treating chronic pain with opioids is to eliminate or significantly curtail abuse of controlled prescription drugs while assuring proper treatment when indicated. Urine drug testing (UDT) has been shown to be a useful approach in identifying patterns of compliance, misuse, and abuse. However, significant controversy surrounds the diagnostic accuracy of UDT performed in the office (immunoassay) and the requirement for laboratory confirmation with liquid chromatography tandem mass spectrometry (LC/MS/MS).

STUDY DESIGN: A diagnostic accuracy study of urine drug testing.

STUDY SETTING: The study was performed in an interventional pain management practice, a tertiary referral center, in the United States.

OBJECTIVE: The objective of this study was to compare the results of UDT of immunoassay in-office testing (index test) to LC/MS/MS (reference test).

METHODS: One-thousand participants were recruited from an interventional pain management program. Urine sample was collected from all the consecutive patients with demographic information. Immunoassay testing was performed by a nurse at the location, laboratory assessment was performed with LC/MS/MS. Results of the index test were compared to the reference test in all patients. The sensitivity, specificity, false-positive, and false-negative rates, and index test efficiency (agreement) were calculated.

RESULTS: Overall, results showed that confirmation was required in 32.9% of the specimens. Agreement for prescribed opioids was high with the index test (80.4%). The reference test of opioids improved the accuracy by 8.9% from 80.4% to 89.3%. Non-prescribed opioids were used by 5.3% of patients. The index test provided false-positive results for non-opioid use in 44% or 83 of 120 patients. For illicit drugs, the false-positive rate by index test was 0% for cocaine, whereas it was 2% for marijuana, 0.9% for amphetamines, and 1.2% for methamphetamines.

LIMITATIONS: The limitations include a single site study utilizing a single POC kit and a single laboratory, as well as technical sponsorship.

CONCLUSION: The UDT with immunoassay in an office setting is appropriate, convenient, and cost-effective. Compared with laboratory testing for opioids and illicit drugs, immunoassay in-office testing had high specificity and agreement, demonstrating the value of immunoassay drug testing. Because of variable sensitivity, clinicians would be well-advised to take a cautious approach when interpreting the results.

CLINICAL TRIAL: NCT01052155.