In confirmatory testing for urine drug screening, which method is commonly used?

• A. Gas or liquid chromatography & mass spectroscopy
• B. Depends on the lab
• C. 6-monoacetylmorphine (6-MAM)
• D. Specific to heroin, very short half-life

Answer: (A)

In confirmatory testing for urine drug screening, the standard approach is chromatography coupled with mass spectrometry. This setup provides high specificity because the sample is first separated into its components, and then each substance is identified by its unique mass spectrum. By comparing the observed spectra to trusted reference standards, labs can definitively confirm which drug is present and at what level, greatly reducing false positives that can occur with initial screening tests.

Immunoassay screens are typically used first for speed and cost, but they can give cross-reactivity or false-positive results. GC-MS or LC-MS are the gold standard for verification because they offer precise identification and quantitation, which is essential for accurate interpretation.

A heroin-specific marker like 6-MAM can indicate heroin use, but it represents a single substance marker rather than a general confirmatory method for all drugs. The phrase that it depends on the lab reflects practical variation, but the widely used confirmatory method across many labs is GC-MS or LC-MS.