Impact of Lowering Confirmatory Test Cutoff Value in Pre-Enlistment Urine Cannabinoids Screening: About Five Years' Experience in the French Gendarmerie

Abstract

The guidelines for screening of urinary cannabinoids require that all specimens testing positive should be confirmed by gas chromatography-mass spectrometry at a confirmatory test cutoff value of 15 ng/mL of 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THCCOOH). To assess the impact of lowering the confirmatory test cutoff value on the diagnostic sensitivity and efficiency of a cannabinoid testing program, the results of 986 confirmation analyses of positive screening tests, conducted in the framework of medical fitness examinations prior to enlistment in the French Gendarmerie between January 1, 2005, and December 31, 2009, were retrospectively studied. If the confirmatory test cutoff value of THCCOOH is set at 5 ng/mL instead of 15 ng/mL as recommended by guidelines, the number of confirmed results increases by 25.2%. The positive predictive value of the initial screening test rises from 63.9 to 80.0%. Only one true-positive applicant has appealed. His THCCOOH urinary concentration, which was incompatible with passive cannabis smoke exposure, was confirmed by another laboratory. The use of a confirmatory test cutoff value lower than that recommended significantly increases the diagnostic sensitivity of the screening program for urinary cannabinoids without altering its specificity.

Interest of adjusting urine cannabinoids to creatinine level to monitor cannabis cessation therapy in heavy smokers with psychiatric disorders

“…Monitoring cannabis cessation or consumption is generally based on the determination of cannabinoids in urine, using automatized immunoassay methods with cut‐offs values of 20 or 50 ng/mL to discriminate between positive and negative samples. Fifty ng/mL is a widely used cut‐off with strong sensitivity and specificity, but it has been suggested that a screening test threshold of 20 ng/mL could improve sensitivity while preserving the specificity . Some covariates affect the urinary concentration of cannabinoids, including consumption frequency, intensity and period, body fat, body mass index (BMI), and urine dilution according to solute intake and hydration status.…”

“…Fifty ng/mL is a widely used cut-off with strong sensitivity and specificity, but it has been suggested that a screening test threshold of 20 ng/mL could improve sensitivity while preserving the specificity. 8 Some covariates affect the urinary concentration of cannabinoids, including consumption frequency, intensity and period, body fat, body mass index (BMI), and urine dilution according to solute intake and hydration status. However, sensitivity and specificity of the analytical method used could also affect the detection window of these compounds.…”