Drug testing is a very important part of maintaining workplace safety for many companies. However, there are sometimes employees who try to cheat at drug tests. Find out what you need to know about catching cheats in the urine drug testing process.

Adulteration of a urine specimen can occur through substitution of another specimen, use of a flushing or detoxification agent, or through the addition of a masking agent to the voided specimen. It occurs most frequently when unsupervised specimen collection occurs in the context of pre-employment screening. (Learn more in "Drug Test Types: 5, 7, and 12 Panel Urine Screening Differences and Reasons to Use".) Urine specimen integrity testing will identify many abnormalities consistent with adulteration and SAMHSA requires additional testing of specimens with abnormal chemical characteristics or physical appearance.

What is an adulterant?

An adulterant in workplace drug testing refers to a substance that an individual can add to a specimen to mask the presence of a substance or its metabolite in the specimen in order to hide evidence of use. According to federal guidelines, an adulterated specimen is a urine specimen that contains either an endogenous substance at an abnormal physiological concentration or a substance that is not a normal constituent of the specimen.

Adulteration most commonly occurs when a specimen collection is not directly observed, typically during a pre-employment screening program. There are three primary ways that individuals attempt to cheat on a drug test: substitution of the urine specimen with drug-free urine or synthetic urine, which can be purchased from multiple sources; ingestion of commercially available products to speed elimination of drugs; and addition of an adulterant to a specimen after collection.

Substituted urine

Substitution of drug-free urine and synthetic urine is difficult to detect. Synthetic urine has a similar pH, specific gravity, and creatinine composition to normal urine, but synthetic urine lacks other metabolites normally found in urine, such as cortisol. Specific tests for these substances can be ordered to verify the integrity of a specimen if there is suspicion of substitution (Learn more in "POCT vs Lab Testing: What is the Difference?").

Detoxification and elimination agents

Advertised products for detoxification or elimination frequently contain caffeine or a diuretic that increases urine output, which are intended to produce a dilute urine and reduce the concentration of drugs or metabolites below the drug detection cut off level. Commonly advertised products include Ready Clean Drug Detox Drink and Absolute Detox XXL. These agents also require the individual to drink a large amount of water. Herbal teas and water both reduce drug concentrations significantly, and can potentially change a positive test to a negative result.

However, at the same time the drug or metabolite is diluted, urinary creatinine is also diluted, allowing detection of this tactic. Drinking as little as two quarts of fluid will decrease the creatinine levels to below the cutoff for a normal specimen. (Learn more in "Drug Detection Cutoffs: What You Need to Know".) There is also a small risk of water intoxication if the drug user ingests too much liquid too fast.

Adulteration of a specimen after collection

There are a number of products on the market that can be added to urine after collection to alter the results, including Klear (a nitrite), Stealth (which consists of peroxidase and peroxide), and Urine Luck (which contains pyridinium chlorochromate). Iodine can also be used to oxidize urine and can destroy metabolites of marijuana. Papain, an enzyme found in papaya, may also reduce the concentration of marijuana metabolites when added to a urine specimen. In addition, some individuals try to adulterate their urine specimens with household chemicals. Although most household methods can be identified by specimen integrity testing, some products like Visine® and isopropanol cannot be reliably detected.

Spotting adulteration

Specimen integrity testing typically detects adulterated specimens that are outside of the normal temperature, pH, specific gravity, and creatinine concentration expected from a freshly voided urine specimen. The Substance Abuse and Mental Health Services Administration (SAMHSA) requires additional testing when a specimen has abnormal physical characteristics or characteristics of an adulterated specimen, including a pH that is less than 3 or more than 11, or a nitrite concentration greater than 500 mg/m.

There are also a number of spot tests available as specially designed urine dipsticks. Specially designed urine dipsticks are available to identify a number of common adulterants, with test pads that detect pH, specific gravity, bleach, creatinine, oxidants, nitrite, chromate, and gluteradehyde. Gluteradehyde based products are one type of adulterant available in widely used cleaning solutions in hospitals and clinics. Use as an adulterant can result in false-negative screening tests for most drugs, but some laboratories offer a method of detection using fluorimetry.

Stealth can be spot tested using a chemical reaction with addition of tetramethylbenzidine and a phosphate buffer solution. Nitrate containing adulterant products interfere with the confirmatory test for marijuana metabolites, but testing for nitrite concentrations due to these products can be performed easily at the initiation of specimen testing. Zinc sulfate has been introduced as a new urinary adulterant, but is not widely used.

It has the potential to invalidate many urine drug tests that are widely used. Two rapid spot tests have been developed to check for adulteration by zinc sulfate. The presence of chromium greater than 50 mg/mL indicates an adulterated specimen and should be confirmed by colorimetry or a general oxidant test. Elemental halogens, including iodine and bromine, can be also be tested by a general test for presence of oxidants and can be confirmed by a number of techniques, including spectrophotometry.