A drug test (also often toxicology screen or tox screen) is a technical analysis of a biological specimen, for example urine, hair, blood, breath, sweat, or oral fluid/saliva—to determine the presence or absence of specified parent drugs or their metabolites. Major applications of drug testing include detection of the presence of performance enhancing steroids in sport, employers and parole/probation officers screening for drugs prohibited by law (such as cocaine, methamphetamine, and heroin) and police officers testing for the presence and concentration of alcohol (ethanol) in the blood commonly referred to as BAC (blood alcohol content). BAC tests are typically administered via a breathalyzer while urinalysis is used for the vast majority of drug testing in sports and the workplace. Numerous other methods with varying degrees of accuracy, sensitivity (detection threshold/cutoff), and detection periods exist.
A drug test may also refer to a test that provides quantitative chemical analysis of an illegal drug, typically intended to help with responsible drug use.
Detection periods The detection windows depend upon multiple factors: drug class, amount and frequency of use, metabolic rate, body mass, age, overall health, and urine pH. For ease of use, the detection times of metabolites have been incorporated into each parent drug. For example, heroin and cocaine can only be detected for a few hours after use, but their metabolites can be detected for several days in urine. The chart depicts the longer detection times of the metabolites. In the case of hair testing, the metabolites are permanently embedded into hair, and the detection time is determined by the length of the hair sample used in the analysis. The standard length of head hair used in the test is 1.5", which corresponds to about 3 months. Body/pubic hair grows slower, and the same 1.5" would result in a longer detection time.
Oral fluid or saliva testing results for the most part mimic that of blood. The only exceptions are THC (tetrahydrocannabinol) and benzodiazepines. Oral fluid will likely detect THC from ingestion up to a maximum period of 6–12 hours. This continues to cause difficulty in oral fluid detection of THC and benzodiazepines.
Breath air for the most part mimics blood tests as well. Due to the very low levels of substances in the breath air, liquid chromatography–mass spectrometry has to be used to analyze the sample according to a recent publication wherein 12 analytes were investigated.
Rapid oral fluid products are not approved for use in workplace drug testing programs and are not FDA cleared. Using rapid oral fluid drug tests in the workplace is prohibited in only: California Kansas Maine Minnesota New York Vermont
The following chart gives approximate detection periods for each substance by test type.
+ Approximate values for detection periods Substance Urine Hair Blood / Oral Fluid Alcohol 6–24 hours Note: Alcohol tests may measure ethyl glucuronide, which can stay in urine for up to 80 hours up to 90 days 12 to 24 hours Amphetamines (except methamphetamine) 1 to 4 days up to 90 days 12 hours Methamphetamine 1 to 5 days up to 90 days 1 to 3 days MDMA (Ecstasy) 3 to 5 days up to 90 days 3 to 4 days Barbiturates (except phenobarbital) 1–4 days or 2–3 weeks up to 90 days 1 to 2 days Phenobarbital 2 to 3 weeks up to 90 days 4 to 7 days Benzodiazepines Therapeutic use: up to 7 days. Chronic use (over one year): 4 to 6 weeks up to 90 days 6 to 48 hours CannabisPassive inhalation: up to 22 minutes** Infrequent users: 7–10 Days Heavy users: 30 to 100 days up to 90 days 2 to 3 days in blood of infrequent users, up to 2 weeks in blood of heavy users However, it depends on whether actual THC or THC metabolites are being tested for, the latter having a much longer detection time than the former. THC (found in marijuana) may only be detectable in saliva/oral fluid for 2 to 24 hours in most cases, though in rare cases has been detected up to 28 days after consumption. Cocaine 2 to 4 days (with exceptions for heavy users who can test positive up to 4/6 weeks, and individuals with certain kidney disorders) up to 90 days 2–10 days, heavy users or individuals with previous substance use 6/8 weeks Codeine 2 to 3 daysup to 90 days1 to 4 days Cotinine (a breakdown product of nicotine) 2 to 4 days up to 90 days 2 to 4 days Morphine 2 to 3 days up to 90 days 1 to 3 days Tricyclic antidepressants (TCA's) 7 to 10 days Detectable but dose relationship not established. LSD1–4 days (including metabolites) up to 90 days 2 to 4 days Methadone 3 days up to 90 days 24 hours Steroids 3 to 30 days PCP 3 to 7 days for single use; up to 30 days in chronic users up to 90 days 1 to 3 days
Types
Urine drug screen
Urine analysis is primarily used because of its low cost. Urine drug testing is one of the most common testing methods used. The enzyme-multiplied immune test is the most frequently used urinalysis. Complaints have been made about the relatively high rates of false positives using this test.
Urine drug tests screen the urine for the presence of a parent drug or its metabolites. The level of drug or its metabolites is not predictive of when the drug was taken or how much the patient used.
Urine drug testing is an immunoassay based on the principle of competitive binding. Drugs which may be present in the urine specimen compete against their respective drug conjugate for binding sites on their specific antibody. During testing, a urine specimen migrates upward by capillary action. A drug, if present in the urine specimen below its cut-off concentration, will not saturate the binding sites of its specific antibody. The antibody will then react with the drug-protein conjugate and a visible colored line will show up in the test line region of the specific drug strip.
A common misconception is that a drug test that is testing for a class of drugs, for example, opioids, will detect all drugs of that class. However, most opioid tests will not reliably detect oxycodone, oxymorphone, meperidine, or fentanyl. Likewise, most benzodiazepine drug tests will not reliably detect lorazepam. However, urine drug screens that test for a specific drug, rather than an entire class, are often available.
When an employer requests a drug test from an employee, or a physician requests a drug test from a patient, the employee or patient is typically instructed to go to a collection site or their home. The urine sample goes through a specified 'chain of custody' to ensure that it is not tampered with or invalidated through lab or employee error. The patient or employee's urine is collected at a remote location in a specially designed secure cup, sealed with tamper-resistant tape, and sent to a testing laboratory to be screened for drugs (typically the Substance Abuse and Mental Health Services Administration 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. To ensure the specimen integrity and to detect possible adulterants, additional parameters are tested for. Some test the properties of normal urine, such as, urine creatinine, pH, and specific gravity. Others are intended to catch substances added to the urine to alter the test result, such as, oxidants (including bleach), nitrites, and gluteraldehyde. 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) or liquid chromatography - mass spectrometry methodology. If requested by the physician or employer, certain drugs are screened for individually; these are generally drugs part of a chemical class that are, for one of many reasons, considered more habit-forming or of concern. For instance, oxycodone and diamorphine may be tested, both sedative analgesics. If such a test is not requested specifically, the more general test (in the preceding case, the test for opioids) will detect most of the drugs of a class, but the employer or physician will not have the benefit of the identity of the drug.
Employment-related test results are relayed to a medical review office (MRO) 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, typically within 24 hours. 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 to determine if there is any legitimate reason—such as a medical treatment or prescription.
On-site instant drug testing is a more cost-efficient method of effectively detecting substance use amongst employees, as well as in rehabilitation programs to monitor patient progress. These instant tests can be used for both urine and saliva testing. Although the accuracy of such tests varies with the manufacturer, some kits have rates of accuracy correlating closely with laboratory test results.
Breath test
Breath testing is a widespread method for quickly determining alcohol intoxication. A breath test measures the alcohol concentration in the body by a deep-lung breath. There are different instruments used for measuring the alcohol content of an individual though their breath. A Breathalyzer is a widely known instrument which was developed in 1954 and contained chemicals unlike other breath-testing instruments. More modern instruments include infrared light-absorption devices and fuel cell detectors.
To get accurate readings on a breath-testing device the individual must blow for approximately 6 seconds and need to contain roughly 1.1 to 1.5 liters of breath. For a breath test to provide an accurate result an operator must take steps such as avoiding measuring "mouth alcohol" which is a result from regurgitation, belching, or recent intake of an alcoholic beverage. To avoid measuring "mouth alcohol" the operator must not allow the individual being tested to consume any materials for at least fifteen minutes before the breath test. In the United States, a driver who refuses to take a breath test can have their driver's license suspended for a period of 6 to 12 months.
Hair testing
Hair analysis to detect addictive substances has been used by court systems in the United States, United Kingdom, Canada, and other countries worldwide. In the United States, hair testing has been accepted in court cases as forensic evidence following the Frye Rule, the Federal Rules of Evidence, and the Daubert Rule. As such, hair testing results are legally and scientifically recognized as admissible evidence. Hair testing is commonly used in the USA as pre-employment drug test. The detection time for this test is roughly 3 months, which is the time, that takes head hair to grow ca. 1.5 inches, that are collected as a specimen. Longer detection times are possible with longer hair samples.
A 2014 collaborative US study of 359 adults with moderate-risk drug use found, that a large number of participants, who reported drug use in the last 3 months, had negative hair tests. The tests were done using an immunoassay followed by a confirmatory GC-MS. For marijuana, only about half of self-disclosed users had a positive hair test. Under-identification of drug use by hair testing (or over-reporting) was also widespread for cocaine, amphetamines, and opioids. Because such under-identification was more common among participants, who self-reported an infrequent use, the authors suggested, that the immunoassay did not have the sensitivity required for such infrequent uses. It is worth noting, that most earlier studies reported, that hair tests found ca. 50-fold higher prevalence of illicit drug use, than self reports.