A Summary of Clinical Interpretation of Urine Drug Tests

What Clinicians Need to Know About Urine Drug Screens.

The article aims to educate clinicians about urine drug testing and how to effectively perform the best urine test. There are several urine tests to detect the presence of drugs including immunoassay, gas chromatography/mass-spectrometry (GC-MS), and liquid chromatography/tandem mass spectrometry (LC-MS). So far, GC-MS and LC-MS have provided greater results of drug detection than immunoassays. One of the methods that testing preparers should consider is cutoff levels. Cutoff levels were established to help minimize false-positive results (passive inhalation of marijuana causing positive results; poppy seeds ingestion causing positive opiate results). Cutoff values of UDT allow a great concentration needed to produce an accurate result. If the result is lower than the cutoff values, it is reported as a negative result.

However, negative results do not always mean there is no presence of drugs. It is important to know the federal cutoff values for substances of abuse. Clinical laboratories may establish different cutoff values for medication adherence. Interpretation based on the cutoff values is also
significant. Another method of UDT is detection times. Detection time is an amount of time that the drug is present in urine and provides a positive test. Drug characteristics and patient factors need to be considered for detection time evaluation. Urine collection is an important step in order to obtain a great result. Characteristics of urine such as colors, PH, temperatures should be observed. People who misuse drugs commonly use various methods to avoid detection of drugs.

The methods used to mask the result are table salt, laundry bleach, toilet bowl cleaner, vinegar, lemon juice, ammonia, or eye drops. Clinicians when collecting results need to observe carefully because those methods can change the results from positive to negative. Specific drugs tested in the urine are amphetamines, cocaine, marijuana, opiates, phencyclidine, benzodiazepines, semisynthetic and synthetic opioids.

Moeller, K. E., Kissack, J. C., Atayee, R. S., & Lee, K. C. (2017). Clinical Interpretation of Urine Drug Tests: What Clinicians Need to Know About Urine Drug Screens. Mayo Clinic Proceedings, 92(5), 774-796. https://doi.org/10.1016/j.mayocp.2016.12.007

Thi Nguyen

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