How accurate are point-of-care urine drug screens in patients taking chronic opioid therapy?

Of the 3414 samples submitted for opiate testing, 2191 tested positive using immunoassay and 2233 tested positive using LC-MS for a total of 42 false-negative results with immunoassay. The positive rate (percentage of samples testing positive by LC-MS) was 65%, and the false-negative rate was 1.9%. Methadone testing produced 17 false-negative results; the positive rate was 10%, and the false-negative rate was 6.1%. The immunoassay false-positive results occurred in patients taking hydromorphone and hydrocodone.

The study was limited by lack of demographic information on the participants.