Testing Explained

Testing can be a confusing business but it doesn't need to be. This section explains key concepts in jargon free, easy to understand English. If you would like more information on a particular topic please contact us.

Drug Abbreviations

Drug testing kits often use an abbreviated drug name rather than listing it in full. This is because space on product packaging and labelling is limited, and listing the full name of ten or more drugs can take up quite a lot of room.

Here is a list of the common drug abbreviations used in the drug testing industry:

Abbreviations

AbbreviationDrug Name
AMPAmphetamine
BARBarbiturates
BUPBuprenorphine
BZOBenzodiazepines
COCCocaine
COTCotinine
EDDPEDDP (2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine)
FTYFentanyl
KETKetamine
MDMA/XTCMDMA/Ecstasy
MTDMethadone
MET/MAMPMethamphetamine
MOPMorphine
OPIOpiates
OXYOxycodone
PCPPhencyclidine
PPXPropoxyphene
TCATricyclic Antidepressants
THCCannabis
TRATramadol
Screening

Modern screening methods are designed to rapidly identify a sample as either negative or presumptive positive if the substance is above a set cut-off concentration. Negative samples are deemed to not require further investigation, whilst samples that are presumed to be positive will require testing by a different analytical technique, known as a confirmation test.

Our screening methods are based on established immunoassay technology and can be conducted in a laboratory or with a rapid diagnostic test at the point of care. Immunoassays use antibodies as reagents to measure the amount of a particular drug or drug group in the sample.

Antibodies bind to the drug by recognising a distinct three dimensional shape. In simplest terms this can be thought of as a key in a lock. The key (drug) has a distinct shape which will only fit into a suitably matched lock (antibody). This concept is shown in figure 1, where each coloured block is a different drug (with a different shape) reacting to a matching antibody.

Testing explained 1

Figure 1: A stylised representation of an antibody recognising one of the shapes. Notice that each shape will only bind to one antibody.

Cut-Off Levels

One of the key concepts within drug testing is the application of a cut-off level. This is the point which segregates a test result as being either positive or negative.

For drug screening tests, a cut-off is chosen that will optimise drug detection but minimise the number of false positive results. It is important to note that a negative sample doesn’t mean that it is drug free; it might contain a drug at an amount that is lower than the defined cut-off.

If a drug test is reported as screen positive or presumptive positive, this merely shows a response, which is usually because a drug is present. It cannot show how much drug was taken or be correlated to any degree of impairment. As this is a screening tool, all presumptive positives require a confirmation test.

Testing explained 2 Testing explained 2 Testing explained 2

Figure 2: A visual representation of a cut-off level and window of detection.

Windows of Detection

The window of detection is the time that a drug can be detected in a biological sample above a specified cut-off for the test being performed. There is a period of time immediately before and after this detection window when the drug will be present in the sample but at an amount below the cut-off.

Tests are designed to be drug or drug group specific and the cut-off level has been determined to optimise detection without giving false positives.

Drugs are detected in oral fluid either from direct deposition in the mouth or by transfer from the blood stream following ingestion and absorption. Any drugs present in the bloodstream are metabolised in the liver before being excreted in the urine. This process results in drugs appearing in the urine later than oral fluid. The drugs are detectable for a significantly longer time in urine than in oral fluid.

The actual time a drug will remain detectable in a sample will depend on some or all of the following:

  • The amount of drug taken
  • How frequently the drug is taken
  • The nature of the drug itself
  • An individual’s metabolism and general health
  • The amount of fluids taken since taking the drug
  • The amount of exercise taken since taking the drug
  • Genetic variations that affect a response to drugs

For example if a person smoked a single spliff the cannabis could remain detectable in urine for no more than 2–3 days and may even be as short as one day depending on the strength of cannabis. However, if their cannabis use is habitual and heavy it is stored in the fatty tissues, resulting in a much wider detection window (sometimes up to 30 days).

The data supplied below acts as a guideline and should be interpreted very carefully due to the large number of factors that can influence the amount of drug over time. The quoted windows of detection indicate how long a drug can be detected. This doesn’t indicate that the drug will be detected for this long in all cases.

Testing explained 3 Testing explained 3 Testing explained 3

Figure 3: A visual representation of a cut-off level and window of detection.

Oral Fluid

The shortest window of detection is found with oral fluid.

DrugDetection Window
Cocaineup to 24 hours

Benzodiazepines

up to 24 hours
Cannabinoids (THC)up to 24 hours
Methamphetaminesup to 24 hours
Opiates
  - Morphine
  - Codeine
up to 1-2 days
  - up to 24 hours
  - up to 1-2 days
Amphetamineup to 1-2 days
Buprenorphineup to 1-2 days
Ketamineup to 1-2 days
Methadoneup to 1-2 days

Urine

Drugs can be detected in urine for longer, and in consequence the window of detection for some drugs can be affected by whether their effects are short or long acting.

DrugDetection Window
Benzodiazepines
  - Ultra short acting
  - Short acting
  - Intermediate acting
  - Long acting

- up to 12 hours
- up to 1 day
- up to 2-4 days
- up to 7 days

Barbiturates
  - Shorter acting
  - Long acting

- up to 1-2 days
- up to 7 days
Methadoneup to 1-2 days
Amphetaminesup to 1-3 days
Methamphetaminesup to 1-3 days
Buprenorphine/Subutex Analgesic
  - Therapeutic dose
  - Maintenance dose

- up to 1-3 days
- up to 10-12 days
Cannabinoids (THC)up to 1-4 days
Cocaineup to 2-3 days
Opiatesup to 2-3 days
Ketamineup to 3-5 days
Tramadolup to 3-5 days

Hair

Hair provides a historic record of drug use, and detection windows are based entirely on hair length. It takes about 14 days for the drugs to appear in the hair shaft, and moving away from the scalp, every 1cm of hair length approximates to a one month window of detection.

Cross Reactivity

A screening test uses established immunoassay technology to measure the amount of a particular drug or drug group in the sample. Antibodies bind to the drug by recognising a distinct three dimensional shape. In simplest terms this can be thought of as a key in a lock. The key (drug) has a distinct shape which will only fit into a suitably matched lock (antibody). Once the antibody is bound to the drug a colour change occurs, the greater the intensity of this colour change the larger the volume of the drug.

Some drug families share a common shape and so an antibody raised to recognise a drug within that group will detect or cross react with all of the drugs within the family.

There are many hundreds of thousands of drugs available worldwide, many of which are broken down by the body into drug metabolites. With so many over the counter (OTC) and prescription only medicines (POM) available, there is a possibility that some of these drugs and their metabolites might have a similar 3-dimensional shape to other drugs and will be detected by the immunoassay. For this reason it is standard practice to perform a confirmation test and request details of a donor’s declared medication after a presumptive positive screening result.

Testing explained 4 Testing explained 4 Testing explained 4

Figure 4: A drug family can share a common shape to which an antibody will bind. Here four different drugs share a triangular section and therefore bind to the top portion of the antibody.

Confirmation

A confirmation test is able to definitively detect individual compounds by matching them to a commercially prepared reference standard using one of the following:

  • GC-MS (Gas Chromatography – Mass Spectrometry)
  • GC-MS/MS (Gas Chromatography – Tandem Mass Spectrometry)
  • LC-MS/MS (Liquid Chromatography – Tandem Mass Spectrometry)

Confirmation tests provide qualitative results of drugs and/or drug metabolites present in the sample.

Drugs are rapidly metabolised in the body to aid excretion and detection of the resulting metabolites indicates drug use by the donor. Sometimes it is only the metabolites that are positive in a confirmation test. For example, heroin is rapidly broken down to 6-monoacetylmorphine (6-MAM) and cocaine is rapidly broken down to benzoylecgonine. Detection of these metabolites demonstrates use of heroin and cocaine respectively. Only a confirmation test would allow the laboratory to make the distinction between illicit, prescription medicines or over the counter medication.

Confirmation results are expressed as positive or negative and are legally defensible.

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