Sep 2, 2026
What a Negative Urine Immunoassay Does Not Exclude
A negative urine immunoassay does not exclude every drug or exposure. Assay targets, cutoffs, timing, dilution, and device effects shape the result.
Read guideEVIDENCE LIBRARY
Urine Drug Testing
Evidence-focused guides to urine drug screening, immunoassay limitations, confirmatory testing, cutoffs, specimen validity, and defensible interpretation.
Aug 26, 2026
Presumptive Urine Drug Screens: Why Confirmation Matters
Learn why urine immunoassay screens are presumptive, how false positives and negatives occur, and when confirmation or methamphetamine isomer testing matters.
Read guide