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.