Conventional approaches to drug testing rely on a primary screening step followed by a secondary confirmation.  Best practice dictates that the secondary confirmation step utilize a separate methodology than the initial screening step and have improved sensitivity and specificity.  This approach is widely utilized in clinical, pre-employment, and forensic settings.  Despite the standard adoption of this approach, issues can occur that impact the accuracy of results.

“False Positive Carbamazepine Results by Gas-Chromatography Mass Spectrometry and VITROS 5600 Following a Massive Oxcarbazepine Ingestion” was published in the July 2018 issue of The Journal of Applied Laboratory Medicine.  The case study highlights unique circumstances that affected both screening and confirmatory methods for urine drug testing.