Workplace drug testing is typically conducted and interpreted how?

• A. Specimens are analyzed only by GC-MS with no immunoassay screening.
• B. Specimens (urine, saliva, hair) are analyzed with an initial immunoassay screening followed by confirmatory GC-MS or LC-MS; results interpreted against cutoffs.
• C. Only blood samples are used, and results are interpreted without cutoff values.
• D. Hair analysis alone provides definitive results without screening.

Answer: (D)

Workplace drug testing relies on a two-step approach to ensure accuracy and defensibility. First, specimens such as urine or saliva (and sometimes hair) undergo an initial immunoassay screening to quickly flag potential positives. If the screening is positive or inconclusive, a confirmatory test using a highly specific method like GC-MS or LC-MS is performed. The final result is interpreted against predefined cutoff values to determine a true positive or negative. Hair analysis by itself is not definitive and is not used as the sole basis for workplace decisions; it can provide a longer-term exposure window but still requires confirmatory testing. This combination of screening plus confirmatory testing with clear cutoffs is the standard practice.