At a DOT urine collection, the specimen is divided into two sealed bottles: Bottle A (primary) and Bottle B (split). The laboratory tests Bottle A; Bottle B is stored unopened.

If the MRO verifies Bottle A as positive, adulterated, or substituted, the employee may ask the MRO, within 72 hours of being notified, to have Bottle B tested at a different HHS-certified laboratory (49 CFR 40.171).

• If Bottle B reconfirms the result, the verified result stands.
• If it does not, the MRO cancels the test.