In people who use illicit drugs or who abuse drugs, the metabolites (breakdown by-products) of these drugs are found in the bloodstream. These breakdown by-products are carried to hair follicles through the blood supply and deposited there over a period of time. Hair follicle drug tests involve collecting a sample of hair and carrying out tests on it which try to detect the presence or absence of these metabolites. Therefore, a hair drug test can give a history of drug use and the types of drugs abused. Metabolites deposited in hair follicles can usually be detected for a period of up to 90 days.
This drug testing method has a lot of advantages but it also has its disadvantages.
Advantages of Hair Follicle Drug Tests
1. Non-Invasive: The method of collection of the sample for hair drug tests does not cause inconvenience, pain or embarrassment to the sample donor. A little amount of hair from any part of the body but usually from the head is simply cut off as close to the root of the hair as possible.
2. Easy Sample Collection and Handling: Hair samples do not require special procedures or mediums for collection and transportation unlike some other types of samples. Hair can simply be collected into any container and does not need to be refrigerated or preserved in any way.
3. Dependable and Accurate: Hair drug testing is effective and highly accurate because it detects drug metabolites deposited inside the hair shaft. These metabolites cannot be removed by washing the hair and cannot simply be added to the hair. Therefore, drug testing using hair prevents the contamination of samples and diminishes the possibility of false-positive or false-negative results.
4. Detects Chronic Drug Use: Metabolites of drug use are deposited in hair follicles over a period of time and thus, hair testing can reveal the length of time over which drug use has take place. Metabolites are detected in hair for up to 90 days. It helps to differentiate between one-off occurrences or addiction.
5. Checks Sample Adulteration: It is a lot more difficult to tamper with hair so as to pass a hair drug test or to modify the results.
6. Longer Window of Detection: Hair drug testing allows for detecting previous drug use in an individual even after he or she has stopped drug use. This is significant in situations where the knowledge of a history of drug use is essential. It is usually required in important and critical positions where present or past drug use in any form is unacceptable.
7. Time-Saving: Hair drug tests can save time by allowing for the detection of drug use over months by using a single test instead of requiring multiple samples over that same period of time like in other types of drug tests.
Disadvantages of Hair Follicle Drug Tests
1. Cannot Detect Recent Drug Use: The deposition of drug metabolites in hair follicles takes place over time. Therefore, hair drug tests usually cannot detect drug use that occurs about 1 to 7 days before the test.
2. Requires Laboratory Facilities: A hair drug test requires a laboratory for it to be carried out. This makes hair drug tests more expensive than carrying out saliva or urine drug tests.
3. Longer Waiting Period for Test Results: Hair drug tests usually require 2-3 days to be completed. Therefore, it cannot be used in situations in which the result of the drug test is needed urgently.
4. Depends on the Presence of Hair and Length of Hair Sample: An individual may shave off all head, facial and body hair to avoid providing samples for a hair drug test. Even where hair samples are available, if the hair has been recently cut or trimmed it may affect the results. This can occur where the person has stopped using the drugs being tested for; this means that later growth of hair may not contain the drug metabolites. Also, the person may currently be abusing drugs which will not be detected because they have not yet been incorporated into the new hair.
5. Difficulty in Testing for Some Drug Types: Some drugs such as marijuana do not bind easily to hair and thus, testing for these drugs use may be difficult using hair drug tests.
See more: The Pros and Cons of Oral Drug Tests
See more: Advantages and Disadvantages of Urine Drug Tests