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What is a split specimen test?
Last Updated: 09/24/2026
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.
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