Table 4. Evaluation of multiple criteria to identify recent cannabis smoking (within 6 h of first sample collection) in sequential THC-glucuronide positive samples.
Parameter%Difference ≥40% absolute change%Difference ≥50% absolute change%Difference ≥60% absolute change%Difference ≥50% absolute change and 1st sample ≥1 μg/mg%Difference ≥50% absolute change and 1st sample ≥2 μg/mg%Difference ≥50% absolute change and 1st sample ≥3 μg/mg%Difference ≥40% absolute change and 1st sample ≥2 μg/mg
OverallTP29292829292729
TN109114117114115116110
FP148587612
FN7677687
Total159157157158157157158
Sensitivity80.682.980.080.682.977.180.6
Specificity88.693.495.993.494.395.190.2
Efficiency86.891.192.490.591.791.188.0
FrequentTP22222122222022
TN107112114112112113107
FP126466511
FN5455465
Total146144144145144144145
Sensitivity81.584.680.881.584.676.981.5
Specificity89.994.996.694.994.995.890.7
Efficiency88.493.193.892.493.192.489.0
OccasionalTP7777777
TN2232333
FP2212111
FN2222222
Total13131313131313
Sensitivity77.877.877.877.877.877.877.8
Specificity50.050.075.050.075.075.075.0
Efficiency69.269.276.969.276.976.976.9