To detect or exclude the presence of commonly abused and/or illegal drugs. This may be carried out for a number of reasons including screening for pre-employment purposes or to comply with a drug rehabilitation programme.
Drugs of Abuse
- If you apply for a job where drug screens are carried out as a routine. People with drug and alcohol problems have worse records for accidents and absenteeism; for this reason some employers screen job applicants prior to appointment.
- If you have admitted having a drug problem and are enrolled in a detoxification or drug rehabilitation scheme where testing is part of the programme.
- If you believe you may have taken a drug accidentally or been given a drug without consent (e.g. drink spiking).
- If you are admitted to hospital in an emergency and doctors think that your treatment could be improved if drug abuse could be proved or excluded.
- If you take part in a sport at a professional level.
- If you apply for an insurance policy – some companies perform limited drug screening on applicants.
- For legal reasons (e.g. child custody cases).
Some prescription and over-the-counter drugs may give a positive screening result; prior to testing, indicate any medications that you have taken and/or for which you have prescriptions.
The presence of various classes of abused drugs can be detected. The analysis usually starts with a screening test where the drug group (e.g. opiates – heroin, morphine, codeine etc) is detected; positive results are then followed up by a more specific test which identifies the individual drug taken (e.g. morphine).
A drugs of abuse ‘screen’ usually covers the more commonly abused drug groups which are the opiates, benzodiazepines, barbiturates, cannabinoids, amphetamines (including Ecstasy) and cocaine. Drugs used in the treatment of opiate addiction (methadone and buprenorphine) and ‘legal highs’ are also often detected.
How is the sample collected for testing?
A random urine sample is usually collected for the detection of drugs of abuse although they can be detected in blood, sweat and saliva and hair samples can be used on rare occasions. If the outcome of the test may have legal implications you may be asked to provide a sample under supervised conditions and certify that it's your sample.
Is any test preparation needed to ensure the quality of the sample?
Certain prescription and over-the-counter drugs may give a positive screening result. Prior to testing, you should declare any medications that you have taken recently and/or for which you have prescriptions so that your results can be interpreted correctly.
How is it used?
Analysis of urine specimens for drugs of abuse only gives information about current or recent drug use. A urine specimen taken more than 2-3 days after a period of “drug abuse” is likely to be negative on screening for most substances. Cannabis is the notable exception to this, and can remain at detectable concentrations in urine for up to 2 weeks or even longer after prolonged exposure.
The approximate periods of time during which some drugs of abuse can be detected in urine are listed below. There is a lot of variation from one person to another and detection will depend on the dose taken, the frequency and way the drug was taken, the concentration of the urine (influenced by how much fluid has been drunk) and the speed at which the drug is broken down and removed from the body, so these periods are only a guide.
Drug LengTH of time it can be detected in urine after ingestion Alcohol Up to 1 day Amphetamines & Ecstasy 1-3 days Barbiturates 1-3 days Benzodiazepines 1-3 days Cannabis (THC) Up to 2 weeks Cocaine 1-3 days Codeine 1-2 days Dihydrocodeine 1-2 days Heroin (morphine) Up to 1 day Methadone 1-3 days
Drugs of abuse can also be detected in other body fluids such as saliva but with saliva the period of detection is much shorter than in urine.
When is it requested?
What does the test result mean?
A result reported as 'positive' in a screening test suggests that the concentration of drug present is greater than a specified cut-off concentration for that particular drug. Most UK laboratories use the same concentration to define a positive result and conform to the Substance Abuse and Mental Health Services Administration (SAMHSA) guidelines.
The sensitivity of drug detection will be reduced in urine specimens which are very dilute. At concentrations below the cut-off limit, the drug will normally be reported as not detected. Excessively dilute urine specimens may be rejected as not valid.
Is there anything else I should know?
Certain foods and prescribed drugs can interfere and give false positive results with the initial screen for certain drug groups (e.g. taking codeine or eating poppy seed bread can give a positive opiate result) and for this reason positive results are usually confirmed by a second, more accurate laboratory method before they are reported.
I’ve tested positive for opiates but took painkillers containing codeine?
I think I had my drink spiked on a night out, how easy is it to tell?
The majority of drugs used in Drug Facilitated Sexual Assault cases (so called ‘date rape’ or ‘drink spiking’), such as ketamine, GHB (gammahydroxybutyrate) and rohypnol (flunitrazepam),act very quickly and pass out of the body within 24 hours. This rapid clearance from the body makes it important that medical advice is sought as quickly as possible and that a urine specimen is collected as soon as possible, and certainly within 24 hours.
Can I buy home tests to detect drugs of abuse?
Yes, home or Point of Care tests are available usually by mail order. These tests usually only detect the drug groups (e.g. opiates) rather than the individual drugs such (e.g. morphine). They do not have the second confirmatory step which is required to eliminate false positive results and the quality of the measurement is generally inferior to that provided by an NHS laboratory. Home testing alone is not suitable where legal action might be considered.