Pre-employment urine drug screening: examining trends in THC-COOH positivity rates post-legalization of recreational cannabis in California – a retrospective review

Abstract Background: This study examines trends in delta-9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH) positivity rates in pre-employment urine drug screenings at a single university-based hospital occupational medicine clinic from 2017 to 2022, following California’s recreational cannabis legalization in 2016, with sales beginning officially on January 1, 2018. Methods: Retrospective analysis of 21,546 de-identified urine drug screenings from 2017 to 2022 was conducted. Initial screening used instant urine drug immunoassays (50 ng/mL cutoff for THC-COOH), followed by confirmatory gas chromatography-mass spectrometry (15 ng/mL cutoff).