Evaluation of the Usefulness of An Oxycodone Immunoassay in Combination with a Traditional Opiate Immunoassay for the Screening of Opiates in Urine

Oxycodone is a semisynthetic opioid analgesic largely prescribed for post-operative and chronic pain management. The introduction of a slow release formulation of oxycodone has led to its frequent abuse and to an increase in emergency cases related to oxycodone overdose. Until recently, oxycodone testing has been confined to gas chromatography-mass spectrometry (GC-MS) analysis because the widely used automated opiate immunoassays poorly react to this compound. We investigated the utility of a new oxycodone immunoassay as a screening procedure to eliminate inappropriate GC-MS testing of negative urine specimens. We analyzed 96 urine specimens using GC-MS and two immunoassays, CEDIA((R)) opiates and DRI((R)) oxycodone assays from Microgenics, on a Hitachi 917 analyzer. The GC-MS allowed us to detect codeine, hydrocodone, hydromorphone, morphine, oxycodone, and oxymorphone following enzymatic hydrolysis and derivation by acetylation. The combination of the two immunoassays gave the best performance (98% sensitivity and specificity) when considering a positive result from GC-MS for any of the opiates. Considering positive GC-MS results for oxycodone or oxymorphone only, the oxycodone immunoassay resulted in two false-positives and one false-negative (50 ng/mL cutoff). Using these immunoassays for screening before GC-MS analysis provides a reduced opiate GC-MS workload without compromising quality.