What is the difference between the various drug testing methods?
Hair, saliva, urine and fingerprint drug tests are all used in a number of ways, by different testers, to detect different substances within different timeframes. If you need a drug or alcohol test, it’s important to understand which should be used when.
Saliva testing is one of the most affordable testing methods, and while it offers significant benefits in the right circumstances, it has its limitations. Here, we explain the differences between a drug test with hair and saliva testing, taking you through how they work, what they are used for, the benefits and more.
Hair Testing
How does it work?
Hair strand testing for alcohol or drugs identifies traces of alcohol or drugs both inside and outside a shaft of hair. When the sample arrives in the laboratory for testing, it is first washed to remove external contamination before any testing takes place: the detection of metabolites is further confirmation of actual consumption as opposed to contamination. In the case of drugs, the test allows the lab to measure the number of drugs and their metabolites in the hair shaft. For alcohol, it establishes whether certain biomarkers of alcohol consumption are present in the hair. Learn more about the process here.
What are hair tests used for?
Hair drug and alcohol testing is a reliable means of establishing an individual’s history of drug or alcohol consumption, distinguishing between casual and chronic use, and chronicling usage over a period of up to 12 months.
What drug and alcohol use does hair testing show?
The exact number of substances varies from laboratory to laboratory. At Cansford, we have the ability to test for 120 substances: alcohol, plus drugs in categories including antidepressants, steroids, new psychoactive substances (i.e. ‘legal highs’,) opiates and more. Contact us for a full list.
What are the cut-offs for hair testing?
A cut-off is the point which determines whether a test result is positive or negative. When the amount of drugs or alcohol in the system are below the cut-off, they are considered as “Not Detected” or “Negative”. When they are above the cut-off, they are considered “Detected” or “Positive”.
Cut-offs vary depending on the substance being tested for - and may also vary depending on the methodology used and the laboratory conducting the analysis. Recommended cut-off levels can be found in the Society of Hair Testing Guidelines.
What is the collections process for hair testing?
Hair samples are collected under controlled conditions, and by a trained collector. They are immediately wrapped and labelled, before being sealed in a tamper-proof envelope and sent to the testing laboratory. Read more about the collections process here.
What are the benefits of hair testing?
A drug test with hair is chosen for its accuracy and its ability to determine long term patterns of misuse. It offers the widest window for detection of any testing method: 0-6 months for alcohol, and 7 days to 12 months (or more) for drugs, depending on the length of the hair.
What are the limitations of hair testing?
Hair samples can be subject to external contamination, as a result of being in close contact with drug users. However, as noted before, if procedures are followed properly, the risk of false positives through external contamination is low.
While hair testing can paint a long term picture of drug use, it cannot pinpoint the exact date of usage, nor can it confirm the context of use - unless the lab is informed of anything that might affect the test results.
What else do you need to know?
Hair testing is one of the most expensive forms of drug testing, however, its accuracy is second to none - and it can be conducted even if the subject is bald, or if they try to cheat the system. In addition, a hair test can replace many separate urine or oral fluid tests, making it an ideal sample to prove abstinence.
Saliva Testing
How does it work?
Saliva testing identifies the presence of a drug or its metabolites within a saliva sample. It can be conducted in two different ways: either using immunoassay screening, or with liquid chromatography and mass spectrometry. Find out more here.
What are saliva tests used for?
Saliva drug tests analyse samples for drug use within the last couple of days, making them a common choice for random drug screenings, day-to-day testing of subjects who are under close supervision, and as complementary screening alongside hair tests. A combination of hair and saliva tests effectively confirms or denies both long term and short term substance misuse.
What drug and alcohol use does saliva testing show?
While home saliva testing kits will only recognise the presence of a small number of drug types, laboratory tests will pick up a range of drugs in various groups, from amphetamines to Z-drugs.
There are two types of oral fluid drug test: screening tests (or presumptive tests), which are qualitative tests to establish whether a drug is present, and confirmation tests (or definitive tests): quantitative tests confirming which drugs are present, and in what quantity.
What are the cut-offs for saliva testing?
Recommended upper limits for cut-off concentrations for different substances can be found in Appendix D of the European Guidelines for Workplace Drug Testing in Oral Fluid. These recommended limits vary depending on whether the test is a screening or confirmation test, and are significantly lower than those used in urine testing.
What is the collections process for saliva testing?
While home testing kits are available, they may produce different results to laboratory testing due to lower sensitivity levels and the lack of a chain of custody. A laboratory test involves the collection of the sample under supervised conditions, before analysis is conducted. Immunoassay screening can be carried out immediately after sample collection, and positive samples are securely transported to the lab for further analysis. Where a “Point of Care” (POC) test is used, it is important to have a laboratory confirm the initial results: false positives are more common with these types of tests compared with laboratory tests.
What are the benefits of saliva testing?
Saliva testing is a quick and non-invasive way of testing for substance misuse. Because of its non-invasive nature, testing can be conducted under supervision - meaning a lower risk of tampering. It is an affordable testing method, and the results of a screening test can be analysed instantly, establishing whether it should be sent to the lab for confirmation.
What are the limitations of saliva testing?
The window of detection is low, compared with hair testing: saliva tests can only detect the use of drugs within the previous couple of days. Because of this short testing window, it is impossible to tell with a saliva test whether the subject is a regular drug user.
Contamination can also be an issue: food, drink and medicines may interfere with the results, especially when the recommended collection procedure is not followed. In addition, while the range of drugs that can be detected in oral fluid is close to what is possible with urine and hair, the different matrices have different susceptibilities to external factors like food and medication. If there are worries about particular foodstuffs or current medications, it is best to contact the laboratory before sampling.
What else do you need to know?
Saliva testing is commonly used for workplace drug tests due to its affordability. The full European guidelines, from collection through to interpretation of results, can be found here.
