Drug tests in the United States can be divided into two general groups, federal mandated and general workplace.

Federal mandated drug testing started when President Ronald Reagan enacted via executive order, that federal workers refrain from using illegal substances. Subsequent federal legislation required drug testing within the executive branch of government as well as "safety sensitive" occupations within the trucking, mass transit, rail, airline, marine, and oil and gas pipeline sectors. Drug testing guidelines and processes, for federally mandated drug testing, are established and regulated (by the Substance Abuse and Mental Health Services Administration/ SAMHSA, formerly under the direction of the National Institute on Drug Abuse / NIDA. Referred to as the NIDA-5, or standard SAMHSA six panel test, the laboratory based urine test includes marijuana, opiates (codeine and heroin), amphetamine/methamphetamine, and PCP. Unfortunately, these test classes were established decades ago, with little major revision, and do not account for current drug usage patterns. For example, SAMHSA / DOT tests exclude semi-synthetic opioids, such as oxycodone, oxymorphone, hydrocodone, hydromorphone, etc., and other prescription pain medications widely abused in the United States.

While SAMHSA/NIDA guidelines only allow laboratories to report quantitative results for the "NIDA-5" on their official NIDA tests, many drug testing laboratories and on-site tests now offer a wider or "more appropriate" set of drug screens which may be more reflective of current drug use patterns. As noted above, these tests include semi-synthetic pain killers such as Oxycodone (Oxycontin, Percocet), Oxymorphone, Hydrocodone (Vicodin), Hydromorphone; benzodiazepines (Valium, Xanax, Klonopin, Restoril) and barbiturates.

Other drugs, such as meperidine (Demerol), fentanyl, propoxyphene, and methadone are not commonly tested for in most pre-employment situations, however, are being increasing included in random testing.

A confirmation test (usually GC/MS, or LC/MS/MS) can tell the difference between chemically similar drugs such as methamphetamine and methylenedioxymethamphetamine (MDMA or ecstasy).

Common types of drug tests

Urine drug screen

When an employer requests a drug test from an employee the employee is typically instructed to go to a collection site. The employee’s urine is collected at a remote location in a specially designed secure cup, sealed with a tamper resistant tape, and sent via express delivery service to a testing laboratory to be screened for drugs (typically SAMHSA 5 panel).

The first step at the testing site is to split the urine into two aliquots. One aliquot is first screened for drugs using an analyzer that performs immunoassay as the initial screen. If the urine screen is positive then another aliquot of the sample is used to confirm the findings by gas chromatography - mass spectrometry (GC-MS) methodology. All test results are relayed to an MRO (Medical Review Office) where a medical physician reviews the results. If the result of the screen is negative, the MRO informs the employer that the employee has no detectable drug in the urine. However, if the test result of the immunoassay and GC-MS are non-negative and show a concentration level of parent drug or metabolite above the established limit, the MRO contacts the employee and to determine if there is any legitimate reason - such as a medical treatment or prescription.

On-site instant drug testing is becoming more widely used in states allowing it as a more cost-efficient method of effectively detecting drug abuse amongst employees, as well as in rehabilitation programs to monitor patient progress. These instant tests can be used both in urine testing, as well as saliva testing, and the accuracy of the tests depends on the manufacturer, but there are some kits out there that are extremely accurate, holding a 99% correlation to the GC/MS laboratory testing.

About 5% of the all pre-employment urine samples tested in the U.S. turn out positive for drugs. The percentages are much higher for post-accident and/or reasonable suspicion testing.

The efficacy of urine testing is debatable due to systematic cheating (adulteration and/or substitution of the specimen). Sample substitution and adulteration occur frequently, and both are effective methods of avoiding would-be positive tests. While most laboratories performing drug screens test for adulterants routinely, they can not keep pace with the various forms of adulterants available.

There are many reasons that an individual may produce a dilute urine specimen, the majority of which are the result of normal physiological processes (e.g. pregnancy, diabetes, etc.) specific circumstances, or an individual's personal characteristics (e.g., body type, sex, race, athleticism). Because dilute specimens are relatively common for these reasons, neither the HHS Guidelines nor the U.S. Department of Transportation Procedures for Transportation Workplace Drug and Alcohol Testing Programs permit further processing of negative and dilute specimens. Specific gravity testing can be done to identify whether or not the sample is of dilute nature.

Hair alcohol testing 

As the hair grows, it absorbs special markers called fatty acid ethyl esters (FAEEs) and ethyl glucuronide (EtG) into its structure, which remain in the hair indefinitely. These markers are only produced when there is alcohol in the bloodstream, such that the more markers there are, the more alcohol you have consumed.

Tests detecting both FAEE and EtG levels have been used by UK courts. Trimega is the 1st company to commercialise this testing in both the UK and US judicial system is Trimega Laboratories of London. The company also is the only company in the world that can provide testing of both ETG and FAEE at the same time therefore increasing accuracy of the results.

Analysis of hair samples has many advantages as a preliminary screening method for the presence of toxic substances deleterious to health after exposures in air, dust, sediment, soil and water, food and toxics in the environment. The advantages of hair analysis include the non-invasiveness, low cost and the ability to measure a large number of, potentially interacting, toxic and biologically essential elements. Hence, head hair analysis is now increasingly being used as a preliminary test to see whether individuals have absorbed poisons linked to behavioral health problems.

In contrast to other drugs consumed, alcohol is not deposited directly in the hair. For this reason the investigation procedure looks for direct products of ethanol metabolism. The main part of alcohol is oxidized in the human body. This means it is released as water and carbon dioxide. One part of the alcohol reacts with fatty acids to produce esters. The sum of the concentrations of four of these fatty acid ethyl esters (FAEEs: ethyl myristate, ethyl palmitate, ethyl oleate and ethyl stearate) are used as indicators of the alcohol consumption. The amounts found in hair are measured in nanograms (one nanogram equals only one billionth of a gram), however with the benefit of modern technology, it is possible to detect such small amounts. In the detection of Ethyl Glucuronide, or EtG, testing can detect amounts in picograms (one picogram equals 0.001 nanograms).

However there is one major difference between most drugs and alcohol metabolites in the way in which they enter into the hair: on the one hand like other drugs FAEEs enter into the hair via the keratinocytes, the cells responsible for hair growth. These cells form the hair in the root and then grow through the skin surface taking any substances with them. On the other hand the sebaceous glands produce FAEEs in the scalp and these migrate together with the sebum along the hair shaft (Auwärter et al., 2001, Pragst et al., 2004). So these glands lubricate not only the part of the hair that is just growing at 0.3 millimeters per day on the skin surface, but also the more mature hair growth, providing it with a protective layer of fat.

FAEEs (nanogram = one billionth of a gram) appear in hair in almost one order of magnitude lower than (the relevant order of magnitude of) EtG (picogram = one trillionth of a gram). It has been technically possible to measure FAEEs since 1993, and the first study reporting the detection of EtG in hair was done by Sachs in 1993.

In practice, most hair which is sent for analysis has been cosmetically treated in some way (bleached, permed etc.). It has been proven that FAEEs are (surprisingly) not significantly affected by such treatments (Hartwig et al., 2003a). FAEE concentrations in hair from other body sites can be interpreted in a similar fashion as scalp hair (Hartwig et al., 2003b).

Saliva drug screen / Oral fluid-based drug screen

Saliva / oral fluid-based drug tests can generally detect use during the previous few days. Saliva or oral fluid based drug tests are becoming more prevalent because of their convenience and the fact that they are very difficult to adulterate. Furthermore, on-site oral based tests in particular enable the implementation of random testing programs, proven to be the most effective type of drug screening. Testing is usually performed by employers, for either pre-employment, random, post-accident, reasonable suspicion, or return-to-duty testing. Oral fluid based testing most closely mimics results found with blood and is preferable for detecting on-the-job drug use or in post-accident applications in this case because the degree of intoxication can be approximated based on the amount of substance.

Detection in saliva tests begins almost immediately upon use of the following substances, and lasts for approximately the following times:
Alcohol: 6-12 hours
Marijuana and hashish (THC): 12-24 hours
Cocaine (including crack): 1 day
Opiates: Up to 2-3 days
Methamphetamine ("Tweak," "crank," "ice") and ecstasy (MDMA, "Molly") : Up to 2 to 4 days.
Benzodiazepines: From time of ingestion up to 2 to 3 days
Amphetamines 3 days
Phencyclidine (PCP) 3 days

NOTE: Saliva tests are highly sensitive and detection times can vary considerably based on the cutoffs used.

Sweat drug screen

Sweat tests are patches attached to the skin to collect sweat over a long period of time (1-4 Hours). These are almost exclusively used by child protective services, parole departments, and other government institutions concerned with drug use over long periods, when urine testing is not practical.

Drug testing methodologies

The different types of drug tests are tested in very similar ways. Before testing the sample, the tamper-evident seal is checked for integrity. If it appears to have been tampered with or was damaged in transit, the laboratory rejects the sample and does not test it.

One of the first steps for all drug tests is to make the sample testable. Urine and oral fluid can be used "as is" for some tests, but other tests require the drugs to be extracted from urine beforehand. Strands of hair, patches, and blood must be prepared before testing. Hair is washed in order to eliminate second-hand sources of drugs on the surface of the hair, then the keratin is broken down using enzymes. Blood plasma may need to be separated by centrifuge from blood cells prior to testing. Sweat patches are opened up and the sweat collection component is soaked in a solvent to dissolve any drugs present.

Laboratory-based drug testing is done in a two-tiered fashion using two different types of detection methods. The first is known as the screening test, and this is applied to all samples that go through the laboratory. The second, known as the confirmation test, is only applied to samples that test positive during the screening test. Screening tests are usually done by immunoassay (EMIT, ELISA, and RIA are the most common). A "dipstick" drug testing method which could at some future time provide screening test capabilities to field investigators has been developed at the University of Illinois.

After a suspected positive sample is detected during screening, the sample is flagged and tested using the confirmation test. Samples that are negative on the screening test are discarded and reported as negative. The confirmation test in most laboratories (and all SAMHSA certified labs) is performed using mass spectrometry, and is extremely precise but also fairly expensive to run. False positive samples from the screening test will be negative on the confirmation test. Samples testing positive during both screening and confirmation tests are reported as positive to the entity that ordered the test. Most laboratories save positive samples for some period of months or years in the event of a disputed result or lawsuit. For workplace drug testing, a positive result is generally not confirmed without a review by a Medical Review Officer that will normally interview the subject of the drug test.

Types of testing

Pre-employment drug testing

This is by far the most common type of drug test used by businesses, however, it is also the least effective. It is considered to be an "intelligence test" by drug testing professionals. It has the advantage of being inexpensive, since only one test per employee needs to be paid for by the company. However, since most pre-employment drug testing is urine-based and subject to sample adulteration or substitution, the effectiveness of this approach has been questioned by federal legislators. Some organizations have a witness in the room at the time of the testing, but the privacy implications of this, as well as the potential for shy bladder syndrome has limited the use of witnesses outside jails and drug treatment programs. Companies and testing centers that do not use witnesses normally disconnect sources of water from the testing room to discourage dilution, and if there is water in the toilet, it is dyed blue. Other countermeasures, such as making the donor change into a gown, may also be used.

Random drug testing

Random drug testing is the most effective format. In the USA, random drug testing is used by a growing number of corporations, drug rehab centers, prisons, the military, police and fire departments, government agencies, and more recently, schools. It may also be used on teens by their parents, or mandated to be performed at school. The objective of a random drug test is deterrence, as the threat of detection is much higher versus other testing methods. Various random selection methods are used, ranging from drawing names out of a hat to using random number generators.

Critics of random testing claim that random drug testing introduces a presumption of guilt, and is a violation of privacy if the drug user is not actually intoxicated during working hours. In addition, urine-based random testing is more likely to catch cannabis users, since THC metabolites are fat soluble and have a longer duration in the body than those of many other drugs.

Post-incident drug testing

Post-incident drug testing is not a very commonly administered test compared to the other two, but the financial ramifications of not testing employees after an accident (or other incident) on the job makes this test worthwhile for most businesses. The point of this test is not necessarily to cause the employee to lose his or her job, but rather to protect the company from liability in the event that the individual is under the influence at the time of the accident. If drugs or alcohol are detected in any significant quantity, the argument can be made in court that the individual was intoxicated on the job, and for that reason, the company should not be held liable for injuries sustained by the employee. This argument, however, can only reasonably be made if blood or oral fluid / saliva testing is used. Urine, hair, or sweat based testing can only detect past drug use. Depending upon the facts of each case, this may help a company avoid litigation completely or may do nothing to help their case. DUI testing would also fall into this category. Another time this type of test may be used is if an employee shows up for work intoxicated, has alcohol on his or her breath, or appears to be impaired in some other way.

The sample should follow chain of custody requirements and should always be sent to a lab after collection. Positive on-site tests that may affect an employee's position or situation should always be followed up with a laboratory test before any action is taken against the employee.

Drug testing methods

Urine drug testing

Urine drug test kits are available as on-site tests, or laboratory analysis. Urinalysis is the most common test type and used by federally mandated drug testing programs, yet likely the least effective.

The main advantages of urine-based drug test kits is/are (1.) the ease at which they can be "cheated" via simple adulteration or substitution, unless specimen collection is directly observed, (2.) inability to detect current / on-the-job drug abuse, (3.) the need for bathroom facilities, and (4.) with respect to SAMHSA-5, or NIDA-5, the inability to test for drugs commonly abused/mis-used in current society.

Saliva drug testing

Saliva (oral) drug test kits are easy for the tester to collect the specimens. There is no need for a bathroom to administer the tests. Saliva drug testing tends to detect recent drug use. Also these drug tests are harder to adulterate than the urine drug tests since the sample can be obtained under direct supervision. Depending on the test, up to 8 different drugs could be detected. This method is the best method for determining recent use and is a potential indicator of impairment.

A disadvantage of saliva based drug testing is that it is not approved by SAMHSA for use with DOT / Federal Mandated Drug Testing. Oral fluid is not considered a bio-hazard unless there is visible blood, however, it should be treated with care.

Spray (sweat) drug testing

Spray (sweat) drug test kits are considered by some to be "non-invasive". It is very easy to collect the specimen and no bathroom is needed for taking the specimen. The detection window is long and usually can detect drug use up to a couple of hours. These drug tests are relatively tamper proof since they are hard to manipulate. A laboratory is not required for analysis.

The main disadvantage of spray or sweat based drug testing is the fact that they are open to contamination. Also large variations of sweat production rates of possible donors make some results inconclusive. There is not much variety in these drug tests since they are not as popular as urine or saliva drug testing kits. Their prices tend to be higher per test conducted. One main disadvantage of this testing method is the limited number of drugs that can be detected, and the ability to produce instant results.

Hair drug testing

Hair drug testing can provide a much longer window of detection, which is useful for highly safety-critical positions where there is zero tolerance of drug usage. Even if the person being tested has a shaved head (perhaps in preparation for the test), hair can also be taken from almost any other area of the body. This includes facial hair, the underarms, arms, and legs.

Though it is often claimed that hair test cannot be tampered with by any known means, it has been shown that this is simply untrue. For example, THC does not readily deposit inside epithelial cells so it is possible for cosmetic and other forms of adulteration to reduce the amount of testable canaboids within a hair sample.

Legality and ethics of mandatory drugs testing


United States

Mandatory drug testing entered American life through two separate historical routes. The first was through the common law system, employing precedents philosophically derived from the idiosyncratic rules governing the "king's forest" and the "king's highway". From these arcane precepts are derived the laws which allow legal authorities to detain and test persons under suspicion of driving under the influence of a psychoactive drug.

The second route was more recently constructed and originated from an incident that occurred in the US Navy. After a plane crashed onto the carrier deck of the USS Nimitz in 1981, killing and injuring dozens of personnel, drug testing was instituted immediately. The results revealed a large substance-abusing cohort within the ranks of enlisted persons and officers. As a result of this single incident, the Secretary of the Navy instituted an intensive drug testing and regulation program. These interventions were then adopted by other branches of the service over a three-year period. From these actions was derived the concept of a "drug-free workplace". In consultation with his drug-czar, Dr. Carlton Turner, President Ronald Reagan issued Executive Order 12564. In doing so, he instituted mandatory drug-testing for all safety-sensitive executive-level and civil-service Federal employees. This was challenged in the courts by the Natl. Treasury Employees Union. In 1988, this challenge was considered by the US Supreme Court. A similar challenge resulted in the Court extending the drug-free workplace concept to the private sector. These decisions were then incorporated into the White House Drug Control Strategy directive issued by President George H.W. Bush in 1989.