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What happens after a non-negative drug test: an employer's decision guide
The steps between a reactive screen and a final employment decision — what the lab does, what the MRO does, and what you should not do until the process is finished.
A drug test result is not a single moment — it is a chain of steps, and what you can do with it depends on which step it is at. Acting too early is one of the most common employer mistakes, and it is also one of the most costly ones.
This guide walks HR and designated employer representatives through the path from an initial reactive screen to a verified result your policy can address — without supervisors improvising discipline on preliminary notifications.
For DOT programs, Medical Review Officer review is mandatory. For non-DOT programs, using an MRO is strongly recommended before you treat any non-negative outcome as final.
The result pipeline most employers do not visualize clearly
A drug test result is not a single moment — it is a chain of steps, and what you can do with it depends on which step it is at. Acting too early is one of the most common employer mistakes, and it is also one of the most costly ones.
Step one: the initial screen. Most labs use immunoassay screening technology. A reactive (non-negative) screen result means the sample showed a reaction above the cutoff for a particular substance. It is not a positive. It is the beginning of further testing, not the end of the process.
Step two: confirmation. Any reactive screen is sent to GC-MS (gas chromatography-mass spectrometry) for confirmation. The confirmation uses a different methodology and a separate cutoff. A sample can screen reactive and confirm negative. Employer action before confirmation is not appropriate.
Step three: MRO review (for DOT collections, mandatory; for non-DOT, strongly recommended). The Medical Review Officer receives the confirmed result and contacts the donor to determine whether a legitimate medical explanation exists — a valid prescription, a verifiable medical procedure, or another documentable reason. If a valid explanation exists, the MRO may report the result as negative. If not, the MRO reports it as verified positive.
Step four: final result to employer. The verified positive (or other final result status) is reported to the DER or designated employer contact. This is the result on which employment action is based. See our MRO role guide for employers for what to expect during review.
Result types and what each means
Verified positive: confirmed and MRO-reviewed. Take action consistent with your policy.
Negative dilute: specimen was valid but too dilute to be a reliable negative. DOT employers may request a recollection under direct observation. Non-DOT employers should follow whatever their written policy specifies.
Positive dilute: specimen was dilute and still confirmed positive. Treated as verified positive.
Refusal: same consequences as verified positive under DOT. Under non-DOT policy, consequences are defined by your written program.
Substituted: creatinine and specific gravity indicate the specimen could not be consistent with human urine. Treated as a refusal under DOT.
Adulterated: specimen contains a substance not expected in human urine, indicating tampering. Treated as a refusal under DOT.
Invalid: result cannot be used; re-collection under direct observation is typically ordered.
Cancelled: the test cannot be used due to a collection or lab error. Not a violation — donor must retest.
What to document and when to act
Document the dates and steps throughout the process. For post-accident and reasonable suspicion collections, document the observations that triggered testing before the collection happens, not after the result comes back.
Take employment action only after you have a final verified result — not on a screen, not on a lab confirmation alone, and not on rumors or assumptions. If your TPA or MRO is handling the process, wait for their notification before acting.
If a verified positive leads to removal from safety-sensitive duty, return-to-duty planning runs through a Substance Abuse Professional — see SAP and return-to-duty for employers.
Keep collections defensible end to end
We handle qualified collections and chain-of-custody paperwork—your TPA and MRO finish the result path before you act.