How to Detect Drug Test Cheats

How to Detect Drug Test Cheats

As drug test adulteration becomes more sophisticated, so do detection methods

Mar 13, 2019
Raeesa Gupte, PhD

The Drug-Free Workplace Act, passed in the U.S. in 1988, prohibits federal employees, contractors, and grantees as well as those in federally-regulated industries or safety and security-related industries from possessing or using controlled substances. Although not mandated, several private employers have also adopted a drug-free workplace policy. Outside of the workplace, drug testing is regularly employed in healthcare, sports, and forensics.  

People cheat on drug tests for a variety of reasons—to retain their jobs, keep their medals, avoid going to prison, and to maintain their spotless reputations. In fact, cheating drug tests has essentially become an industry in its own right.

This article provides an overview of the methods of drug testing, commonly screened legal and illegal substances, windows of detection, methods of adulteration or substitution, and ways to detect whether test samples have been tampered with.

Types of drug tests

Drug tests commonly follow a two-step process. First, immunoassays provide a qualitative “yes” or “no” answer to whether the drugs being tested are present in the biological sample. Immunoassays use antibodies to detect the presence of specific drugs and/or their metabolites. If drug concentrations in the sample are below the designated threshold value, it indicates a negative result. If the initial screen yields a positive result, samples are processed for further confirmation and quantification. In the second confirmatory step, gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS), or LC tandem mass spectrometry (LC-MS/MS) is performed on the samples. These techniques separate the compounds in the sample, which are then identified based on their unique molecular fingerprints and quantified.

Drug testing can be performed on several types of biological samples, each with their own pros and cons, as outlined in Table 1.

Biological matrix

Pros

Cons

Urine

  • Non-invasive collection
  • Large sample volumes
  • Ease of drug/metabolite detection
  • Fairly large window of detection
  • Most commonly used matrix due to availability of validated techniques
  • Easy to tamper
  • Cannot detect long-term drug use

Hair

  • Non-invasive collection
  • Supervised collection limits tampering and adulteration
  • Detects long-term drug use
  • Cosmetics (shampoos and dyes) do not alter results of most drugs 

Saliva/Oral Fluid

  • Non-invasive collection
  • Supervised collection limits tampering and adulteration
  • Small sample volume
  • Short window of detection
  • Subjects need to be monitored 10-30 minutes prior to sample collection

Blood

  • Samples can be obtained from incapacitated subjects
  • Detects recent drug use
  • Most accurate measure of alcohol levels
  • Invasive collection requires trained personnel
  • Very short detection window

Sweat

  • Non-invasive collection
  • Can detect recent drug use (sweat wipes) or cumulative use over several weeks (sweat patches)
  • Tampering leads to visible puckering of patches
  • Few facilities with expertise in analyzing sweat tests
  • Limited number of drugs validated for testing
  • Risk of accidental or deliberate removal of patch

Table 1. Pros and cons of performing drugs tests on various biological matrices


How long do drugs stay in the body? 

Workplace drug testing is based on the Substance Abuse and Mental Health Administration’s 5-panel immunoassay commonly referred to as SAMHSA-5. This panel traditionally tests five categories of drugs: amphetamines, marijuana, cocaine, opiates, and phencyclidine (PCP). Most commercially available drug screens also test for alcohol, barbiturates, benzodiazepines, MDMA (ecstasy), and synthetic opioids (oxycodone, hydrocodone, buprenorphine, and methadone) in addition to the SAMSHA-5 panel. Table 2 shows the average duration that these drugs can be detected in various biological matrices.

Substance

Urine

Hair

Saliva/Oral Fluid

Blood

Sweat

Alcohol

10 - 12 hours

Up to 90 days

Up to 24 hours

Up to 6 hours

N/A

Amphetamines

2 - 4 days

Up to 90 days

1 - 48 hours

Up to 48 hours

7 - 14 days

Methamphetamine

2 - 5 days

Up to 90 days

1 - 48 hours

Up to 48 hours

7 - 14 days

Barbiturates

Up to 7 days

Up to 90 days

N/A

Up to 48 hours

N/A

Benzodiazepines

Up to 7 days

Up to 90 days

N/A

Varies 

N/A

Marijuana 

1 - 30 days

Up to 90 days

Up to 24 hours

Up to 36 hours

7 - 14 days

Cocaine

1 - 3 days

Up to 90 days

1 - 36 hours

Up to 48 hours

7 - 14 days

Codeine

2 - 4 days

Up to 90 days

1 - 36 hours

N/A

7 - 14 days

Morphine 

2 - 5 days

Up to 90 days

1 - 36 hours

Up to 20 hours

7 - 14 days

Heroin 

2 - 3 days

Up to 90 days

1 - 36 hours

Up to 20 hours

7 - 14 days

Oxycodone

2 - 4 days

N/A

N/A

N/A

N/A

Hydromorphone

2 - 4 days

N/A

N/A

N/A

N/A

Methadone

3 days

N/A

N/A

N/A

N/A

Propoxyphene

6 - 48 hours

N/A

N/A

N/A

N/A

Phencyclidine (PCP)

5 - 6 days

Up to 90 days

N/A

Up to 24 hours

7 - 14 days

MDMA (Ecstasy)

Up to 48 hours

N/A

Up to 24 hours

Up to 24 hours

N/A

Table 2. Average durations over which different drugs can be detected in various biological matrices.

 

Ways to beat a drug test

Owing to privacy concerns, urine collection is often performed unobserved. Therefore, urine samples are most amenable to manipulation in the following ways: 

     1. Substitution

To avoid a positive result, test-takers substitute their urine with synthetic urine or drug-free urine from another person or an animal. 

     2. Dilution

Dilution of urine samples takes many forms. Water or other liquids may be added to the collected sample to dilute it. Alternatively, test-takers may drink lots of water or consume products marketed as “detox” drinks that claim to rid the body of drugs anywhere from a few hours to a few days prior to sample collection. The mechanisms of action of these products are often unknown but likely involve dilution of urine in order to lower the concentration of drug(s) below detection limits. Their side effects may vary from changing urine color to causing intestinal issues and nausea. Some so-called detoxifiers also claim to render a negative result on hair tests following varying periods of abstinence.

     3. Adulteration

In vitro adulteration involves addition of substances to urine after sample collection that will interfere with the test results. A slew of adulterants, including household substances (vinegar, detergent, bleach, iodine, isopropyl alcohol, and eye drops), food items (lemon juice and soda) and commercially available chemicals (nitrite, glutaraldehyde, and pyridinium chlorochromate), are regularly used to cheat a drug test. These substances may interfere with the detection of some, but not all drugs on the test panel. For instance, pyridinium chlorochromate (PCC) may reduce detection of morphine and marijuana, but increase sensitivity to amphetamines without affecting the detection of PCP. Depending on the concentration used, glutaraldehyde may produce false-negative results for marijuana, amphetamine, methadone, benzodiazepine, and cocaine metabolites. The mechanism by which adulterants produce false-negative results may vary. Nitrites, peroxides, and chromates may hamper the detection of drugs and their metabolites by oxidizing them, for example, whereas glutaraldehyde may interfere with the enzymes used in certain assays. 

How to detect a tampered drug test

     1. Physicochemical characteristics

Changes in the appearance and odor are usually the first indications of sample manipulation. Dilution of urine by drinking excessive water may produce a clear, almost water-like appearance. In contrast, urine detoxifiers may produce unnaturally colored urine. However, some detoxifiers contain niacin that imparts a natural yellow color and is not flagged as an adulterant. Adulteration with vinegar, bleach, and alcohol can be detected by the distinctive odors they produce. Turbidity or excessive frothing indicates addition of detergents. Because human urine has several known physiochemical values—temperature of 32? - 38? (when freshly collected), specific gravity of 1.002 - 1.02, creatinine concentrations above 20 mg/dL, and pH of 4.5 – 9—deviations from these ranges is indicative of dilution or substitution.

     2. Spot testing for adulterants

Several colorimetric reactions can be used to detect the presence of specific adulterants such as nitrite, PCC, and glutaraldehyde. For instance, hydrogen peroxide turns urine adulterated with PCC brown and potassium permanganate added to urine adulterated with nitrite turns from pink to colorless upon addition of hydrochloric acid. 

     3. Adulteration test strips

Several on-site adulteration detection strips and devices are commercially available. Urinalysis tests such as AdultaCheck (Sciteck Diagnostics) and Intect 7 (Branan Medical) contain individual strips that can detect pH, creatinine, glutaraldehyde, nitrites, PCC, and other oxidants.

The changing landscape of drug test cheating

Positive results on workplace drug testing continue to rise in certain sectors such as transportation and construction. The widening chasm between legalization of marijuana in several states and federal drug-free workplace policies may further spur cheating on drug tests. As the sale of drug-free urine is being banned in some states and several states have pending legislation that would ban the use and sale of synthetic urine, ways to obfuscate drug tests get ever-more creative (e.g., powdered urine kits and home remedies like washing hair three to four times a day with vinegar and salicylic acid). As such, detection methods ultimately end up playing catch-up with the deviousness of drug test cheats.  


Raeesa Gupte, PhD

Raeesa Gupte (@NeuroRaeesa) is a freelance science writer and editor specializing in evidence-based medicine. She discovered her passion for communicating science while writing her PhD dissertation, nurtured it as a postdoctoral scientist, and continues to chase it relentlessly.