False Positive Oxycodone Results

Primary Causes of False-Positive Oxycodone Results

The Centers for Disease Control and Prevention, as reported in MMWR Recommendations and Reports, notes that oxymorphone, the metabolite of oxycodone, can be detected by oxycodone immunoassays and may represent metabolism from actual oxycodone use rather than independent oxymorphone use 1

The American College of Obstetricians and Gynecologists recommends that immunoassay screening tests are presumptive only and susceptible to cross-reactions, requiring confirmation by GC-MS when results are unexpected or will impact clinical decisions 1, 2
Many laboratories now use specific oxycodone immunoassays that detect both oxycodone and oxymorphone, improving detection compared to traditional opiate screens, according to the MMWR Recommendations and Reports 1

The MMWR Recommendations and Reports suggests obtaining a complete medication history, specifically asking about naltrexone, all prescribed opioids, over-the-counter medications, and supplements, before making any clinical decisions 3, 4
Discuss unexpected results with the patient in a non-judgmental manner before ordering confirmatory testing, as this can sometimes yield a candid explanation, as recommended by the MMWR Recommendations and Reports 1

The American College of Obstetricians and Gynecologists recommends requesting GC-MS confirmatory testing before making any consequential clinical decisions, such as dismissing patients from care, making punitive decisions, or assuming medication diversion 1, 2, 3, 5
GC-MS can definitively identify specific opioids and metabolites, distinguishing true oxycodone use from false-positives caused by naltrexone metabolites or other cross-reacting substances, according to the MMWR Recommendations and Reports 1

The MMWR Recommendations and Reports warns that never dismissing patients from care or making punitive decisions based solely on immunoassay results without confirmatory testing, as this constitutes patient abandonment and could have severe adverse consequences 1, 5
The American Journal of Obstetrics and Gynecology notes that false-positive results can have severe consequences, including loss of child custody or legal implications, and recommends being aware of these potential consequences 2, 3