DOT Rule 49 CFR Part 40 Section 40.95
Subpart F - Drug Testing Laboratories
§ 40.95 What are the adulterant cutoff concentrations for initial and confirmation tests?
(a) As a laboratory, you must use the cutoff concentrations for the initial and confirmation adulterant testing as required by the HHS Mandatory Guidelines and you must use two separate aliquots – one for the initial test and another for the confirmation test.
(b) As a laboratory, you must report results at or above the cutoffs (or for pH, at or above or below the values, as appropriate) as adulterated and provide the numerical value that supports the adulterated result.
[65 FR 79526, December 19, 2000, as amended at 73 FR 35970, June 25, 2008]