LC-MS/MS Validation for Drug of Abuse Testing Utilizing a Split Sample Oral Fluid Collection System.

The Substance Abuse and Mental Health Services Administration (SAMHSA) recently authorized oral fluid (OF) as a preferable biofluid for drugs of abuse (DOA) screening compared to urine, and they required that each screening method be confirmed by a laboratory test. We developed a DOA mass spectrometry (MS) assay optimized for undiluted OF as a matching confirmatory test for the EZ-Saliva point of care (POC), split sample, rapid visual test. Using a double isotope ratio standardization, we achieved a limit of detection of <0.3 ng/mL for seven DOAs, with high precision in undiluted patient OF (CV<7.2%), linearity of R² = 0.99, lack of interference (<1.0%) by a panel of interfering compounds at 1000-fold excess, and a dynamic range of 0-850 ng/mL, from a consented population of N=84 self-reported THC users using the collection device (device yield >90%). Stability from degradation exceeded 72 hours. The lateral flow immunoassay strips of the POC exhibited a dose-dependent response, with a 90% sensitivity and 100% specificity for N=22 self-reported, THC patient OF, digitized for quantitation. We conclude that the split sample POC device in combination with the MS assay meets the SAMHSA stated requirements for a POC test with a laboratory confirmation. Split sample collection has significant advantages because it minimizes potential error created by taking a separate OF sample for laboratory confirmation. We recommend scaling to a larger validation study set and quantification of user OF THC levels that correlate with driver impairment levels.