Comparison of Response of DRI Oxycodone Semiquantitative Immunoassay With True Oxycodone Values Determined by Liquid Chromatography Combined With Tandem Mass Spectrometry: Sensitivity of the DRI Assay at 100 ng/ml Cut-Off and Validity of Semiquantitative Value.

Objective: Oxycodone is a widely used opioid for pain management and patient's compliance with therapy is often monitored by using oxycodone immunoassay. The performance of the DRI oxycodone immunoassay was compared with liquid chromatography combined with tandem mass spectrometry (LC/MS/MS) assay.

Materials And Methods: In 48 urine specimens collected from patients taking oxycodone, urinary oxycodone concentrations were determined using LC/MS/MS and the DRI oxycodone immunoassay for application on the Cobas c 501 analyzer (Roche Diagnostics, Indianapolis, IN).

Results: Out of 48 specimens, 14 specimens showed oxycodone value less than 100 ng/ml, seven specimens had low positive values (between 101 and 165 ng/ml) and all other specimens had values 165 to 1789 ng/ml using the LC/MS/MS assay. The DRI oxycodone assay successfully identified all oxycodone specimens with oxycodone concentrations over the 100 ng/ml. In addition, the DRI assay also showed positive response in 11 out of 14 specimens with oxycodone values less than 100 ng/ml. However, semiquantitative values obtained by the DRI assay did not match with true oxycodone and metabolite oxymorphone concentrations combined obtained by using LC/MS/MS.

Conclusions: DRI oxycodone immunoassay at 100 ng/ml is a reliable immunoassay for analysis of oxycodone in urine.