Are some urine drug tests more accurate than others? What is the risk of not confirming immunoassay drug testing?
There are two types of urine drug tests used in clinical practice. Typically a clinician will start by using an immunoassay test, as these are faster and less expensive versus other types, mass-spectrometry gas, or liquid-chromatography. However, immunoassay tests are subject to both false positive and negative results, and are considered “presumptive” tests. Some examples of false positives with immunoassay are quetiapine causing a methadone positive, venlafaxine causing a phencyclidine (PCP) positive, omeprazole causing a cannabis positive, bupropion causing an amphetamine positive, and sertraline causing a benzodiazepine false positive. Many other false positives are possible. Providers inexperienced with urine drug tests have hastily discharged or discontinued opioid therapy in legitimate patients. For this reason, careful assessment and definitive testing by chromatography are essential in certain cases, especially if there is a questionable or unexpected test outcome.