Deceptively Simple Can Urine Samples from CLIA-Waived Urine Drug Screen Devices Be Reused for Confirmatory Testing
Many low-complexity urine drug screen (UDS) devices are approved by the Food and Drug Administration as waived under Clinical Laboratory Improvement Amendments (CLIA) criteria. Labeling instructs patients to urinate directly into the device and also states that positive results should be confirmed. However, the device itself may pose a risk of drug adsorption andor specimen contamination that could affect results in confirmatory assays if specimens are reused. Collecting urine in a separate container before performing the UDS would reclassify the test as nonwaived, negating the conveniences of a CLIA-waived test. Also, patients may be unable or unwilling to urinate in an additional container for confirmatory testing. This study examined reusing urine from a UDS device (NexScreen) for confirmatory testing. 25 patient specimens were pooled and verified to be drug-free. To evaluate drug leaching from the UDS device, 30 mL of this pool was incubated in NexScreen cups, followed by confirmatory testing. To evaluate drug adsorption, 14 representative analytes were spiked slightly over the NexScreen positivity cutoffs, followed by incubation in NexScreen cups and confirmation testing. All negative samples incubated in NexScreen cups remained negative upon confirmation testing, indicating that NexScreen test strips do not contaminate the specimen. For the drug adsorption experiment, 11 of 14 analytes had recoveries of at least 95%, whereas buprenorphine and 11-nor-9-carboxy-tetrahydrocannabinol recovered at 94% and 87%, respectively, suggesting minor adsorption. All analytes recovered above their respective confirmation cutoffs. Urine aliquots from NexScreen cups may be used for confirmatory testing.