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Specimen validity testing

While it is the most common drug testing method, urine testing is not foolproof. With specimen validity testing, we can help ensure the integrity of the test by measuring pH, creatinine and specific gravity (when indicated) and testing for adulterants that may be added to the urine specimen.

Key terminology

The US Department of Health and Human Services (HHS) Substance Abuse and Mental Health Services Administration (SAMHSA) defines drug testing terminology in its Mandatory Guidelines for Federal Workplace Drug Testing Programs and the Medical Review Officer Manual for Federal Agency Workplace Drug Testing Programs. Here are definitions to provide a better understanding of terms related to specimen validity testing:  

Adulterated specimen: A urine specimen containing a substance that is not a normal constituent or containing an endogenous substance at a concentration that is not a normal physiological concentration.

Creatinine is endogenously produced and cleared from the body by the kidneys.  It is a normal constituent in urine. Normal human urine creatinine concentrations are at or above 20 mg/dL.  

Dilute specimen: A urine specimen with creatinine and specific gravity values that are lower than expected for human urine.

Invalid result: Refers to the result reported by a laboratory for a urine specimen that contains an unidentified adulterant, contains an unidentified interfering substance, has an abnormal physical characteristic, or has an endogenous substance at an abnormal concentration that prevents the laboratory from completing testing or obtaining a valid drug test result.

Oxidizing adulterant:  A substance that acts alone or in combination with other substances to oxidize drugs or drug metabolites to prevent the detection of the drugs or drug metabolites, or affects the reagents in either the initial or confirmatory drug test. Examples of these agents include, but are not limited to, nitrites, pyridinium chlorochromate, chromium (VI), bleach, iodine, halogens, peroxidase and peroxide.

pH is the measurement of acid-base. Human urine is usually near neutral (pH 7), although some biomedical conditions affect urine pH. HHS set the program cutoffs for pH based on a physiological range of approximately 4.5 to 9.

Specific gravity is a measure of the density of a substance compared to the density of water.  For urine, the specific gravity is a measure of the concentration of dissolved particles in the urine.  Normal values for the specific gravity of human urine range from approximately 1.0020 to approximately 1.0200.   

Substituted specimen: A urine specimen with creatinine and specific gravity values that are so diminished or so divergent that they are not consistent with normal human urine.

The use of oxidizing adulterants – such as nitrites, chromates and halogens (e.g., bleach and iodine) – is one of the most common ways donors try to “cheat a drug test.” Quest Diagnostics is one of the few laboratories to offer oxidant identification for some of the most common oxidizing adulterants and is available when requested by the customer or Medical Review Officer. We monitor and adjust our testing as necessary when new adulterants become commonplace. All “Invalid” specimens,” based on analytical test results, are automatically tested twice on a different portion of the urine specimen to ensure accuracy. 

This chart shows different kinds of adulterants, ways a urine specimen can be diluted or substituted and products used by donors in attempts to “cleanse” their specimen prior to a urine drug test.