Guideline Resources
Urine Drug Screen Interference
Key Points
Presumptive drug tests, incl. urine immunoassay screens, measure the presence/absence of the target drug/analyte vs. amt; exercise caution when interpreting/responding to results. All tests have some rate of false-positive and false-negative outcomes; new false-positive examples are continuously identified, and tests updated/refined to address limitations. Negative results do not r/o substance use, which could have occurred outside the detection window, be below the cutoff value, be excluded from the test panel, etc. Urine is prone to tampering; may test validity by measuring creatinine concentration, pH level, specific gravity, and adulterants. Use a definitive testing technique such as gas or liquid chromatography–mass spectrometry to detect/quantify specific substances and refine result accuracy, esp. if there are major implications for the pt; definitive test results may be taken as conclusive.
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This epocrates resource is developed by our in-house team of pharmacist and physician editors.
Epocrates Guideline Synopsis Last Update: Apr 12, 2024
Publication Year:
2024
Source:
epocrates
Abbreviations
BZD benzodiazepine
PCP phencyclidine
PPIs proton pump inhibitors
THC delta-9-tetrahydrocannabinol