In DOT or workplace drug testing, if the GC-MS confirmation is negative but the immunoassay screen was positive, what is the final result?

• A. The final result is negative; GC-MS confirmation supersedes the screen.
• B. The final result is positive; screen positive overrides
• C. The sample is sent to a second lab for confirmation
• D. The result is inconclusive and must be repeated

Answer: (A)

In workplace drug testing, the screen is a preliminary, highly sensitive test, while the GC-MS is the confirmatory test that provides definitive identification of the drug. Because the immunoassay can yield false positives from cross-reacting substances, the final result rests on the confirmatory test.

If the GC-MS confirmation is negative, there is no confirmed drug detected at or above the required cutoff, so the final result is negative despite the positive screen. The confirmatory result supersedes the screen because it offers specific, verified identification.

The other options aren’t correct because a positive screen does not override a negative confirmatory result, sending the sample to a second lab isn’t standard practice in this scenario, and an inconclusive outcome isn’t reached when the confirmatory test is clearly negative.