Urine Specimen Validity Testing

No matter how effective substance abuse testing is, individuals will always attempt to beat the test. This may be done by diluting the specimen or by causing a chemical breakdown in the urine through something ingested into the body or something added to the specimen. Donors may also attempt to substitute another substance or clean urine for their own.

Alere scientists have developed testing methodologies to isolate and identify chemicals intended to alter or interfere with test results. Alere provides a specimen validity test panel that determines the levels of creatinine, specific gravity, pH, and general oxidants. A client may elect to perform a specimen validity test that can indicate if a urine specimen has been diluted, substituted, or adulterated in any fashion. Results of these tests will appear on individual drug test result reports if they are abnormal.

A valid result is dependent upon the submission of a valid urine specimen. A valid specimen in this context is one where the concentration of the urine is sufficient to yield a drug result that gives an accurate reflection of the drug content of the urine. Since drug screening identifies drug present equal to or greater than a specific cut-off value, dilution of the urine dilutes the drug in the urine, and there is a concern that the drug may be diluted below the level of the cut-off.

The creatinine level and specific gravity of a specimen combine to determine specimen validity, particularly in determining if a specimen has been diluted. Creatinine is a waste product produced by the body and excreted in the urine. Alere has the capability of determining a quantitative level of creatinine in a urine specimen. A normal urine specimen has a creatinine level greater than or equal to 20 mg/dL. Specific gravity is the density of a substance relative to the density of water and provides an indication of the amount of solid particles dissolved in a urine specimen. Alere can determine a quantitative level of specific gravity in a urine specimen. A normal urine specimen has a specific gravity of greater than or equal to 1.003.

There are three categories of specimen validity related to an unacceptable urine concentration. These three categories reflect the progression in the degree of dilution of the urine specimen.

Dilute: If a urine specimen has a creatinine value less than 20 mg/dL but greater than or equal to 2.0 and a specific gravity of 1.0011 – 1.0029, then the specimen is considered dilute. This dilution can come from either drinking large volumes of liquid before providing a urine specimen, or pouring something into the urine cup at the time of collection.

Invalid: There are two instances where a specimen will be reported as “INVALID” due to the creatinine and specific gravity results. One instance is a urine specimen with a creatinine value less than 2.0 mg/dL and a specific gravity of 1.0011 – 1.0199 (an acceptable specific gravity value); the second instance is a urine specimen with a creatinine level greater than or equal to 2.0 mg/dL and a specific gravity of less than or equal to 1.0010. In both of these instances, the specimen is considered diluted to a greater degree than the “Dilute” result. This type of dilution can come from either drinking large volumes of liquid before providing a urine specimen, or pouring something into the urine cup at the time of collection.

Substituted: If a urine specimen has a creatinine value less than 2.0 mg/dL and a specific gravity of less than or equal to 1.0010 or a specific gravity greater than or equal to 1.0200, then the specimen is considered inconsistent with human urine. This result will prompt the result “SUBSTITUTED.” This can come from either pouring something into the urine cup at the time of collection or providing another liquid that is not urine (apple juice, soda, a clean urine, etc.).

In addition to creatinine and specific gravity, the pH level of the specimen can be used to determine its validity. A pH test determines the degree of acidity or alkalinity of a urine sample. A normal urine specimen has a pH between 5 and 8. Alere’s initial pH test has a range from 5.0 to 8.5. A pH outside this range is tested on the pH meter, our confirmation pH test. If the pH confirmation test yields results that are abnormal, the specimen will be reported as “Invalid: Abnormal pH.” This can occur in two instances. In one instance, the pH by pH meter reading is greater than or equal to 3.0 but less than 4.5. In another, the pH is greater than or equal to 9.0 but less than 11.0. Any specimen with a pH of less than 3.0 or greater than or equal to 11.0 will be reported as “Adulterated,” meaning something has been added to the urine specimen after voiding. Examples of substances which will produce a basic pH (11 or greater) are bleach and ammonia. Examples of substances which will produce an acidic pH (3 or lower) are lemon juice and vinegar.

Finally, a general oxidant test can determine the presence of an oxidizing agent that may have been added to the urine specimen after voiding. If the general oxidant test is positive, the sample will be reported as “Invalid: Possible Oxidant Activity.”

Specimen validity is an evaluation of the validity of the specimen and NOT the validity of the test result. A drug positive result on a report with any of the validity flags is still a valid drug positive result. The greatest issue regarding specimen validity is with negative specimens. A negative result accompanied by any of the above flags is cause for concern.

Alere recognizes that those who abuse drugs often understand the principles of specimen validity and may attempt to alter their urine specimens to avoid detection. Our goal is to provide you with the tools to identify potentially invalid urine specimens.