What Is Specimen Validity Testing?

Specimen validity testing is the evaluation of a specimen to determine whether it is consistent with a normal human specimen. For urine, its purpose is to determine whether adulterants or foreign substances were added, whether the urine was diluted, or whether the specimen was substituted (49 CFR 40.86(a)). In DOT testing, laboratories must conduct validity testing on urine specimens (49 CFR 40.86(b)).

Required urine validity tests. For each primary DOT urine specimen, the laboratory must (49 CFR 40.87):

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

The laboratory must also perform additional validity tests when the specimen shows abnormal physical characteristics, reactions characteristic of an adulterant during drug testing, or a possible unidentified interfering substance or adulterant.

Oral fluid. For oral fluid, validity testing evaluates whether the specimen is consistent with normal human oral fluid and whether adulterants or foreign substances were added or the oral fluid was altered. Part 40 does not require routine validity testing of oral fluid. A laboratory may conduct it if a specimen shows abnormal characteristics, such as unusual odor or color, causes reactions characteristic of an adulterant, or contains an unidentified interfering substance (49 CFR 40.92). A laboratory may test for a biomarker such as albumin or immunoglobulin G (IgG), or for a specific adulterant, and must follow applicable HHS requirements (49 CFR 40.93).

Possible outcomes. Validity testing can lead to a dilute, adulterated, substituted or invalid result. If a specimen is invalid and HHS guidelines direct the laboratory to contact the Medical Review Officer (MRO), the laboratory and MRO decide together whether testing at another HHS-certified laboratory would help (49 CFR 40.87(e) and 40.92(c)).

The FAQs on dilute results and oral fluid versus urine testing cover related topics.