Refusal vs Diluted Result — What's a Refusal?

A drug test result has more shades than 'positive' or 'negative.' Specific terms have specific consequences under Part 40.

Negative

Test came back with no detected substances. No action required beyond recordkeeping.

Negative-Dilute

Specimen had a low creatinine and dilute specific gravity. Per § 40.197:

• If diluted with creatinine ≥ 5 mg/dL: result stands as negative (proceed normally)
• If diluted with creatinine ≥ 2 mg/dL but < 5 mg/dL: MRO directs immediate recollection observed under § 40.67
• If diluted with creatinine < 2 mg/dL: treated as refusal (substitution)

The MRO makes this call. Carrier follows the MRO's direction.

Positive

Test came back with confirmed drug presence above cutoff. MRO interviewed driver; no legitimate medical explanation accepted (driver may have a verified prescription, e.g., for amphetamines). Result is a violation → reported to Clearinghouse, driver removed from safety-sensitive duty, SAP process begins.

Positive-Dilute

Test came back positive with dilution. Treated as a regular positive (proceed with violation processing).

Adulterated

Specimen contained a chemical not normally found in urine, or pH outside normal range. Per § 40.93:

• Adulteration is a refusal
• MRO confirms; reported to Clearinghouse
• Driver removed from safety-sensitive duty

Substituted

Specimen was not actually urine (e.g., water, synthetic urine). Per § 40.93:

• Substitution is a refusal
• MRO confirms; reported to Clearinghouse

Cancellation

Test result is invalid for procedural reasons (chain-of-custody break, lab error). Per § 40.205:

• MRO cancels the test
• Driver may need re-collection
• Cancellation is NOT a violation

Critical: refusal triggers

Per § 40.191, the following are refusals:

• Failure to appear for testing
• Failure to provide a specimen
• Failure to remain at collection site
• Failure to provide observed collection when required
• Adulteration or substitution
• Failure to undergo evaluation after positive
• Failure to participate in SAP process

A refusal is treated the same as a positive test for FMCSA purposes.

CFR citations

• 49 CFR § 40.181
• 49 CFR § 40.185
• 49 CFR § 40.197

How Compass surfaces this

This skill is searchable in the Compass Ask interface and runs against the carrier's actual fleet data when invoked from within the relevant tracker. It is read-only — no actions are taken without explicit user approval.

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