WASHINGTON – A first-of-its-kind study published in the Pain Management issue of AACC’s The Journal of Applied Laboratory Medicine shows that a new drug testing approach dramatically improves detection of illicit benzodiazepine use. This could help to curb abuse of these drugs, which are second only to opioids as a cause of prescription drug overdose deaths in the U.S.

As a result of benzodiazepines’ high potential for abuse, urine drug testing is used among chronic pain patients to ensure that they aren’t illicitly taking benzodiazepines or giving their benzodiazepines to others. However, the main method used for urine drug testing, the immunoassay, commonly fails to detect certain benzodiazepines. This can have grave consequences for patients. A false negative result can allow a patient who is abusing benzodiazepines without a prescription to slip by undetected. Conversely, an incorrect negative result can also make it look like compliant patients are selling or giving away their drugs, and can lead to healthcare providers wrongfully denying patients medication they need.

A team of researchers led by Lindsay A.L. Bazydlo, PhD, of the University of Virginia School of Medicine in Charlottesville, has now developed a method for improving the accuracy of urine drug screen immunoassays. In her lab, Bazydlo’s group uses an immunoassay with a manufacturer recommended absorbance cutoff of 100, meaning that only samples with absorbance values at or above 100 are considered positive. The researchers suspected that this was not catching all positive benzodiazepine results, and dropped their lab’s cutoff to an absorbance of 20 to try to improve their detection rate. Any samples with an absorbance ≥20 underwent confirmatory testing with liquid chromatography-tandem mass spectrometry (LC-MS/MS), a method that is more accurate than immunoassay (but too labor-intensive to serve as a frontline drug screen).

Over the course of two weeks, Bazydlo’s lab received 20 samples with absorbance values above 20 but under the original cutoff of 100. LC-MS/MS testing revealed that, of these 20 samples, 17 out of 20 (85%) were positive. Eleven of the 17 represented patients who were taking benzodiazepines without a prescription and would not have been caught using the original cutoff. The other six patients were taking benzodiazepines as prescribed and would have been wrongly accused of not taking their medication without the additional LC-MS/MS testing.

 “This study demonstrates that our urine benzodiazepine testing false negative rate of 47% can be lowered to 2% by optimizing the absorbance cutoff required for confirmatory testing,” said Bazydlo. “The anticipated clinical impact of using an optimized absorbance cutoff is to minimize the risks of patients being wrongfully denied medication and/or not detecting illicit or dangerous drug use.”

About AACC

Dedicated to achieving better health through laboratory medicine, AACC brings together more than 50,000 clinical laboratory professionals, physicians, research scientists, and business leaders from around the world focused on clinical chemistry, molecular diagnostics, mass spectrometry, translational medicine, lab management, and other areas of progressing laboratory science. Since 1948, AACC has worked to advance the common interests of the field, providing programs that advance scientific collaboration, knowledge, expertise, and innovation. For more information, visit www.myadlm.org.

Launched by AACC in 2016, The Journal of Applied Laboratory Medicine is an international, peer-reviewed publication that showcases the applied research in clinical laboratory science that is driving innovation forward in healthcare.