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.