Drug Testing Glossary

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49 CFR Part 40 (Part 40)

The federal regulation setting out how every DOT drug and alcohol test is collected, analysed, reviewed and reported. Every DOT-regulated industry runs testing through it, and an employer cannot vary it.
49 CFR Part 40 (eCFR) ↗

A

Adulterated specimen

A sample the laboratory found evidence of something having been added to. In regulated testing it is treated as a refusal to test, which carries the same consequences as a positive result.
49 CFR Part 40 (eCFR) ↗

C

Cancelled test

A test that failed procedurally — a broken chain of custody, or a flaw that cannot be corrected. It counts as nothing at all: neither a negative you can rely on nor a positive against you.
49 CFR Part 40 (ODAPC) ↗

Chain of custody

The documented record of everyone who handled your sample between collection and analysis. It exists so a result can be tied to you and to nobody else.
SAMHSA — Forms & guidelines ↗

Confirmatory test

The second, more specific test run on anything the initial test flags. It identifies the individual compound and measures it against a lower cutoff. Both thresholds must be met before a positive can be reported.
49 CFR Part 40 (eCFR) ↗

Control line

The line on a home test that confirms the device worked. If it is missing, the result is invalid however the rest of the device looks — not positive.
FDA — Home use tests ↗

Custody and control form (CCF)

The standard form that travels with a federal test specimen, recording the collector, the specimen identification number, whether the collection was observed, and every signature along the chain.
SAMHSA — Forms & guidelines ↗

Cutoff concentration

The level at or above which a laboratory reports a result as positive. Below it, the result is reported negative even if a trace was detected. A reporting threshold, not a measure of how much was taken.
DOT §40.85 ↗

D

Dilute specimen

A sample more watery than a genuine specimen would normally be. It is a statement about concentration, not about drugs — a sample can be both dilute and negative. Usually leads to another collection.
49 CFR Part 40 (eCFR) ↗

Directly observed collection

A collection watched by an observer of the same gender. Most collections are not observed; the circumstances that justify it are specified in the rules rather than left to a collector's discretion.
49 CFR Part 40 (ODAPC) ↗

F

FMCSA Drug and Alcohol Clearinghouse (Clearinghouse)

The federal database recording drug and alcohol programme violations by commercial drivers. Employers query it, so a recorded violation follows the driver rather than staying with one employer.
FMCSA Clearinghouse ↗

Follow-up testing

A plan of unannounced tests you are placed on after returning to duty. The schedule is given to your employer and never to you — it is meant to be unpredictable.
DOT notice (Mar 2026) — SAP ↗

H

HHS-certified laboratory

A laboratory certified by the Department of Health and Human Services to analyse federal workplace test specimens. As of August 2026, none are certified for oral fluid — only urine.
HHS certified labs (Aug 2026) ↗

I

Initial test

The first, fast, sensitive test run across all samples. It reacts to families of similar compounds, so it flags samples for further work rather than identifying anything specifically. Also called the screening test.
49 CFR Part 40 (eCFR) ↗

Invalid result

A result the laboratory could not produce a usable answer for. It goes through medical review and usually leads to another collection. It is not an accusation.
49 CFR Part 40 (eCFR) ↗

M

Medical Review Officer (MRO)

A licensed physician who reviews drug test results before your employer sees them, checks the paperwork, and contacts you so you can explain a lawful medical reason for a positive.
49 CFR Part 40 (ODAPC) ↗

Metabolite

A compound your body produces while processing a substance. Urine drug tests usually look for metabolites rather than the original drug — a marijuana urine test measures THCA, not THC.
DOT §40.85 ↗

N

Non-negative

Laboratory wording for a sample that the initial test flagged and that now needs confirmation. It means nothing has been established yet. Also seen as preliminary positive or presumptive positive.
49 CFR Part 40 (ODAPC) ↗

O

Oral fluid

The saliva specimen collected by a mouth swab. It has authorised federal cutoffs, far lower than urine, but no laboratory is yet certified to analyse it for federal programmes.
HHS certified labs (Aug 2026) ↗

P

Post-accident testing

Testing required after certain accidents. For commercial drivers, always after a fatality; otherwise only where a citation for a moving violation is issued and someone needed immediate off-scene treatment or a vehicle had to be towed.
49 CFR §382.303 ↗

Prohibited status

A commercial driver's status in the Clearinghouse after a violation. It means they may not perform safety-sensitive functions, including driving commercially, until the return-to-duty process is complete.
FMCSA Clearinghouse ↗

Q

Qualitative test

A test that indicates whether something may be present, without measuring how much. The FDA describes consumer at-home drug tests this way.
FDA — Home use tests ↗

R

Random testing

Testing where names are drawn from a pool by a method the employer cannot influence. Each DOT agency sets a minimum annual percentage of the pool that must be tested.
DOT — random testing rates ↗

Reasonable suspicion testing

Testing based on a trained supervisor's specific, contemporaneous observations of appearance, behaviour, speech or body odour. Rumour, tips and general performance concerns do not meet the standard.
49 CFR Part 40 (ODAPC) ↗

Refusal to test

A category of behaviours, not just saying no. Failing to appear, leaving before the process is complete, not providing a sample, or interfering with one all count — and a refusal carries the same consequences as a positive result.
49 CFR Part 40 (ODAPC) ↗

Return-to-duty test (RTD)

A directly observed test taken after a Substance Abuse Professional confirms you have complied with their recommendations. A negative result is required before you may perform any safety-sensitive function.
49 CFR Part 40 (ODAPC) ↗

S

Safety-sensitive function

The work that federal testing rules attach to. It is broader than the obvious task — for a driver it covers more than time behind the wheel — and each agency defines it in its own rule.
49 CFR Part 40 (eCFR) ↗

Shy bladder procedure

The defined process when someone cannot produce a sufficient urine sample: a period with fluids, and if still unsuccessful, a medical evaluation to establish whether there is a genuine medical explanation. Not an automatic refusal.
49 CFR Part 40 (ODAPC) ↗

Split specimen

The second bottle your sample is divided into at collection. If a positive is reported, you may ask for it to be tested at a different certified laboratory within 72 hours of being notified.
49 CFR Part 40 (ODAPC) ↗

Substance Abuse Professional (SAP)

The qualified professional who evaluates you after a violation, decides what education or treatment you must complete, and confirms when you may take a return-to-duty test. The decision point for going back to safety-sensitive work — not your employer.
DOT ODAPC — SAP ↗

Substituted specimen

A sample with readings inconsistent with human urine. Like adulteration, it is treated as a refusal in regulated testing rather than as a negative result.
49 CFR Part 40 (eCFR) ↗

T

THCA

The marijuana metabolite that urine drug tests actually measure. Named in 49 CFR §40.85 as marijuana metabolites, with a screening cutoff of 50 ng/mL and a confirmatory cutoff of 15 ng/mL.
DOT §40.85 ↗

V

Validity testing

The laboratory's separate examination of whether the sample itself is genuine, undiluted human urine — run alongside, and independently of, the test for drugs.
49 CFR Part 40 (eCFR) ↗

Verified result

A laboratory result that has been through Medical Review Officer review. Until that has happened there is a laboratory result but no verified one, and nothing should be reported to an employer.
49 CFR Part 40 (ODAPC) ↗