Lowering the federally mandated cannabinoid immunoassay cutoff increases true-positive results.
Proposed changes to the Health and Human Services Guidelines for forensic urine drug testing will lower the required cannabinoid immunoassay cutoff concentration from 100 to 50 micrograms/L. We investigated the effect of this change on the sensitivity, specificity, and efficiency of eight cannabinoid immunoassays: Syva Emit d.a.u. 100; Syva Emit II 100; Syva Emit d.a.u. 50; Syva Emit II 50; Roche Abuscreen Online; Roche Abuscreen radioimmunoassay; Diagnostic Reagents; and Abbott ADx. All specimens also were assayed by gas chromatography/mass spectrometry. Lowering the cutoff concentration from 100 to 50 micrograms/L increased efficiencies and sensitivities for all immunoassays, with minor decreases in specificity (1.0-2.6%). There was a 23.2-53.6% increase in the number of true-positive specimens identified. Thus, lowering the cannabinoid immunoassay cutoff concentration from 100 to 50 micrograms/L resulted in detection of a substantial number of additional true-positive specimens, with an accompanying small increase in unconfirmed positive results.
Huestis
M A
MA
Chemistry and Drug Metabolism Section, NIDA, NIH, Baltimore, MD 21224.
Mitchell
J M
JM
Cone
E J
EJ
D002186:Cannabinoids / Q000652:urine*; D005554:Forensic Medicine / Q000331:legislation & jurisprudence*; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007118:Immunoassay / Q000706:statistics & numerical data; D008297:Male; D012680:Sensitivity and Specificity; D015813:Substance Abuse Detection / Q000331:legislation & jurisprudence / Q000379:methods*
D002186:Cannabinoids