What Validity Tests Does a Laboratory Run on a DOT Urine Specimen?

A laboratory runs validity tests on every DOT urine specimen to check whether it is consistent with normal human urine. Under 49 CFR 40.86, the purpose of validity testing is to determine whether adulterants or foreign substances were added, whether the urine was diluted, or whether the specimen was substituted. The rule states that the laboratory must conduct validity testing.

Under 49 CFR 40.87, the laboratory does the following on each primary specimen:

• Measures the creatinine concentration, and also the specific gravity if creatinine is less than 20 mg/dL
• Measures the pH
• Runs one or more validity tests for oxidizing adulterants

Under 40.87(d), the laboratory runs more validity tests when the specimen has abnormal physical characteristics, when the drug tests show reactions or responses characteristic of an adulterant, or when there may be an unidentified interfering substance or adulterant.

Under 40.87(e), if the specimen is invalid and HHS guidelines direct the laboratory to contact the MRO, the two decide together whether testing at another HHS-certified laboratory would be useful in being able to report a positive or adulterated result. Dilute and invalid results are covered in What Does a Negative-Dilute DOT Drug Test Result Mean? and What Does an Invalid DOT Drug Test Result Mean?. Substituted and adulterated results are covered in How Does a Laboratory Identify a Substituted or Adulterated Urine Specimen?.

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