Myth Busters (Continued – #4): My lab result was negative but my instant/point of care test was positive. I need a new cup vendor.

Myth: My lab result was negative but my instant/point of care test was positive. I need a new cup vendor.

Fact: They could BOTH be right! Instant/point of care test results depends on combined activity in a given drug class. The instant test is designed to simply indicate if further testing is needed, and is not a definitive test. It’s like asking someone to let you know when the temperature is 87.3 degrees. He can reach out of the car window and tell you “Well, I think it’s close, but I can only confirm using the thermometer.” Similarly, when the instant urine or saliva result is “positive,” it is indicating that an illegal substance may be found. The sample is then sent to a lab for confirmation—the thermometer is analogous to the mass spectrometer. The gas and liquid chromatography mass-spectrometers are highly specialized instruments that are able to identify individual drug metabolites based on their molecular “fingerprints,” and check the accuracy of the instant test with a high level of specificity. The mass spectrometry analysis will tell you whether, for example, a substance is present as indicated by the instant test, but is not an illegal substance. Conversely, mass spectrometry can tell you that not only was an opiate found, but it was oxymorphone. The mass spectrometry result is the final result.