With DOT-regulated tests, the labs have to abide by the regulations outlined under 49 CFR Part 40.

With that being pointed out, the labs must perform the validity tests outlined under Section 40.91 of the regulations, and must apply the criteria for a "substituted" urine sample under Section 40.93 of the regulations. Theres no minimum or maximum of what they can adhere to - they have to follow the regulations and protocols outlined.
DOT Rule 49 CFR Part 40 Section 40.91 | Department of Transportation

and

DOT Rule 49 CFR Part 40 Section 40.93 | Department of Transportation

As you can see, uric acid is NOT part of the validity tests being ordered to perform, nor there is no standards established for uric acid as there are for creatinine, specific gravity, pH, nitrites, etc.
Burnt Toast Reviewed by Burnt Toast on . Curious situation, testing for the third time!! Hi, so here's my situation. I have a DOT pre-employment test. I tested the first time, 20 days clean and apparently the sample showed up to the lab with the container not sealed, causing the test to be canceled. After I had given the first test, I smoked. Bad choice. But the second test was a week later, I used canadian QuickFix 5.7-1 to be sure I'd pass. The test showed up as having 'Immunoassay interference' and had a result of 'canceled'. Currently my future employer is talking to Rating: 5