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PEHSU Fact Sheet on Marijuana and the Impact on the Pediatric Population (including Perinatal and Adolescent) - Guidance for Healthcare Providers (2018) > Laboratory Testing

Laboratory Testing

posted on Aug 1, 2019
Most standard hospital urine drug screens (UDS) are enzyme immunoassays for THC metabolites. Urine drug screens for marijuana can be positive for several days after acute use weeks after chronic use. A positive UDS does not correlate to symptoms or the level of intoxication but it does reveal systemic exposure. False positives are uncommon but confirmatory testing can be done with high-performance liquid chromatography with mass spectrometry (HPLC-MS) screen. Even though Marinol and Sativex, FDA-approved synthetic cannabinoid THC pharmaceutical products result in positive UDS other cannabinoids, such as, CBD and street synthetic THC may not results in a positive UDS. Positive UDS after passive inhalation of marijuana smoke is very rare but can occur after excessive smoking in small, confined spaces for prolonged periods. Routine lab work and radiography is typically unremarkable.