LOWERING THE FEDERALLY MANDATED CANNABINOID IMMUNOASSAY CUTOFF INCREASES TRUE-POSITIVE RESULTS

Proposed changes to the Health and Human Services Guidelines for foren sic urine drug testing will lower the required cannabinoid immunoassay cutoff concentration from 100 to 50 mu g/L. We investigated the effec t of this change on the sensitivity, specificity, and efficiency of ei ght cannabinoid immunoassays: Syva Emit(R) d.a.u.(TM) 100; Syva Emit I I 100; Syva Emit d.a.u. 50; Syva Emit II 50; Roche Abuscreen(R) Online (TM); Roche Abuscreen radioimmunoassay; Diagnostic Reagents(R); and Ab bott ADx(R). All specimens also were assayed by gas chromatography/mas s spectrometry. Lowering the cutoff concentration from 100 to 50 mu g/ L increased efficiencies and sensitivities for all immunoassays, with minor decreases in specificity (1.0-2.6%). There was a 23.2-53.6% incr ease in the number of true-positive specimens identified. Thus, loweri ng the cannabinoid immunoassay cutoff concentration from 100 to 50 mu g/L resulted in detection of a substantial number of additional true-p ositive specimens, with an accompanying small increase in unconfirmed positive results.