DOT Rule 49 CFR Part 40 Section 40.90
Subpart F - Drug Testing Laboratories
§ 40.90 What criteria do laboratories use to establish that a urine specimen is invalid?
(a) As a laboratory, you must use the invalid test result criteria for the initial and confirmation 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, for a specimen having an invalid result for one of the reasons outlined in the HHS Mandatory Guidelines, you must contact the MRO to discuss whether sending the specimen to another HHS certified laboratory for testing would be useful in being able to report a positive or adulterated result.
(c) As a laboratory, you must report invalid results in accordance with the invalid test result criteria as required by the HHS Guidelines and provide the numerical value that supports the invalid result, where appropriate, such as pH.
(d) As a laboratory, you must report the reason a test result is invalid.
[73 FR 35970, June 25, 2008. Redesignated at 88 FR 27643, May 2, 2023]