Drugs of abuse

Drug of abuse testing can be used for different purposes:

• Clinical screening
• Medico-legal or forensic purposes
• Workplace testing
• Sport (anti-doping)

Clinical screening
Clinical screening mainly aims to determine which drugs or combination of drugs a person may have taken, so that appropriate treatment can be given. The overall effect on a particular person depends on their body’s response to the drugs, the amount and combination, and when each was taken. For example, MDMA is initially a stimulant with associated psychedelic effects, but as it is metabolised and eliminated from the body it can also cause depression of the central nervous system (CNS). Drugs are often combined and/or taken with ethanol (alcohol). If someone drinks alcohol during this period, they will have two CNS-depressant substances in their body, a potentially dangerous combination.

People who may be tested for drugs for clinical reasons include:

• People in A&E with acute health problems that the doctor thinks may be due to drugs: loss of consciousness, nausea, delirium, panic, paranoia, high temperature, chest pain, respiratory failure and/or headache.
• People in A&E after a road accident when the doctor suspects that drugs and/or alcohol may be involved
• A person the doctor suspects may be using drugs
• People being monitored because they are known drug users. This includes legal and illegal use. It may be a general test or one specific to the substance being abused.
• Pregnant women thought to be at risk of drug abuse, or newborn babies showing certain characteristic behaviours.
 
Medico-legal or forensic purposes
Drug testing for medico-legal purposes mainly involves detecting illegal or prohibited drugs in a variety of situations. The procedures for collecting samples in these cases are strictly controlled and documented to guarantee a “chain of custody”.

The person provides a sample, which is closed and sealed with a tamper-evident seal in their presence. Specific chain-of-custody paperwork accompanies the sample throughout the process; everyone who handles and/or analyses the sample signs it and states the reason for transferring the sample. This creates a permanent record of each step of the process. Examples of medico-legal screening include:

• Testing requested by the courts, which usually involves random monitoring of someone who has been imprisoned for illegal drug use. Testing may also be requested in adoption cases to rule out drug use by the parents.
• Child protection services may sometimes require prolonged monitoring of a parent with a history of drug use, to make sure they have not started using again.
• Testing may be required by law when someone has an accident suspected to be linked to alcohol and/or drug use
• Forensic testing uses a variety of body fluids and tissues that can be analysed for numerous drugs during a criminal investigation. The aim may be to establish whether drugs played a role in an incident or crime, as in driving under the influence of drugs, a road accident or rape. Testing may also be done to find out whether someone died of an overdose or of drug-related conditions.

Workplace drug testing
This may be done before employment, at random, after an accident, or if the employer has reasonable grounds to suspect that the employee is using illegal drugs. The main drugs of abuse are tested for, and every positive result is confirmed with another method.

As with medico-legal or forensic use, sample collection and testing procedures for employees are often strictly controlled and documented to maintain the chain of custody. A sample (usually urine) is obtained from the employee in a container that is sealed with a tamper-evident seal in their presence. Specific chain-of-custody paperwork accompanies the sample throughout the process and records everyone who handles and/or analyses the sample. This creates a permanent record of each step of the process.

Screening in sport
While traditional drug tests are carried out on athletes at competitions, the main focus is on doping: drugs or supplements taken to stimulate muscle development and improve strength and endurance. At local level, testing in sport may be limited, but at national and international level it is part of a complex organisation.

The World Anti-Doping Agency (WADA), the US Anti-Doping Agency (USADA) and the International Association of Athletics Federations (IAAF) work together to monitor drug use by athletes at national, international and Olympic level. WADA has a written code that sets rules for uniform drug testing and sanctions across all sports and countries, as well as an extensive list of prohibited substances. Athletes are responsible for any prohibited substance found in their body. Most of the substances tested for are considered positive if detected in any amount, while others, such as caffeine, are prohibited only when present in large amounts. Some substances, such as anabolic steroids (testosterone) and peptide hormones such as erythropoietin, growth hormone and insulin-like growth factor-1, are prohibited but difficult to detect because the body produces them itself. Testing methods must be able to distinguish between the endogenous substance (produced by the athlete’s body) and the one taken from outside.

Screening programmes include random drug tests on athletes during training to look for anabolic steroids, such as testosterone, which stimulate muscle growth. During competitions, testing includes both random tests and tests on all winners, covering substances such as stimulants, narcotics, anabolic agents and peptide hormones. Sports such as archery, gymnastics and shooting also test for other substances such as beta-blockers, which are prohibited in these sports because they lower blood pressure and heart rate.

When is the test requested?
Drug of abuse testing is carried out whenever a doctor, employer, legal body or sports organisation needs to find out whether a person has illegal or prohibited substances in their body.

What does the test result mean?
If a test is positive on initial screening, the person has in their body a substance that belongs to a class of drugs, at a concentration above the set cut-off. If the sample is confirmed positive on the second (confirmatory) test, for example for marijuana, then the person has indeed taken this drug. In some cases this result can be linked to the time since the drug was taken and roughly to the amount, but in most cases this information is not needed. Interpreting when and how much of a drug was taken can be difficult, because the concentration of many drugs varies from person to person with the speed of their metabolism.

If the drug or drugs are not present, or their concentration is below the set cut-off, the result is reported as “not detected”. A negative result does not necessarily mean that the person has never taken drugs. The drug may be present below the set cut-off, it may already have been metabolised and eliminated from the body, or the method used may not detect the specific drug in the sample.

Urine tests detect drug use in the last 2-3 days for amphetamines, cocaine and opiates. Marijuana and its metabolites, cannabinoids, can be detected for several weeks. A hair sample, taken from the part closest to the root, reflects drug use over the last 2-3 months but not the last 2-3 weeks, the time needed for the hair to grow. Saliva shows which drugs have been taken in the last 24 hours. Sweat samples can be collected on a patch worn for several days or weeks, so they reflect drug use at any time during the whole period. These other types of sample are often used for specific purposes. For example, hair samples can be used instead of urine for workplace testing or for people who have caused an accident. Sweat testing can be used for monitoring required by the courts in people who have been in prison for drug use. Blood is the sample most often used for alcohol testing.

Tests for hormones and steroids in sport must be interpreted by people familiar with the testing methods. A negative result indicates a “normal” concentration of the substance in the body. A positive result reflects the presence of the substance above and beyond what the athlete’s body produces. This can be complicated by the fact that each person has their own normal baseline concentration and produces different amounts of hormones depending on the circumstances.

Is there anything else I should know?
The symptoms associated with drug abuse and overdose vary from person to person and from moment to moment and do not necessarily reflect the concentration in the body.

Ethanol can be measured in both blood and exhaled air. The latter is the basis of the breathalyser used by the police.

It is important for the requesting doctor, the law enforcement officer, the forensic doctor, the government agency, the insurance company, the employer and the sports organisation, as well as for the person being tested, to understand exactly what the test is looking for, how it is done and how the result can or cannot be interpreted. The process is not simply a matter of collecting a sample and requesting a drug of abuse test.

Certain prescription and over-the-counter medicines can give positive screening results. When you have a screening test, you must declare every medicine you take and/or have a prescription for, so that the test can be interpreted correctly. In addition, poppy seeds that have not been thoroughly washed can cause a positive opiate screening test if eaten, for example, on a savoury snack or cake. It is advisable to avoid these foods when you are due to have a drug of abuse test.