Common questions about hair testing

Image of Hair CollectionMany tuned in last week to learn from an educational webinar about hair hair testing presented by our laboratory experts, Randy Clouette and Jarod Rowland. Our scientists walked you through the science of hair testing, observed collections, laboratory processes and Quest Diagnostics Drug Testing Index™ data regarding positivity by drug test type. Hair testing is ideal for industries with safety-sensitive workforces and high interaction with the public.

We answered many questions about hair testing during our presentation, but here are a few of the most commonly asked questions.

How much hair is cut for a hair testing drug test?
Quest Diagnostics standard screen usually requires a cosmetically undetectable lock of hair preferably snipped from the back of the head, just below the crown. In general, the amount needed equates to a single row of hairs approximately one centimeter wide.

Can a donor cheat a hair test?
We have not found any adulterants that can beat the test at this time. Moreover, the risk is minimized because every collection is directly and easily observed. In addition, commonly used hair procedures (e.g., shampoos, conditioners, sprays, mousses and gels) have no significant effect on results.

Can tests be run on people with little or no hair?
Yes. Hair can be collected from several locations on the head and combined to obtain the required amount of hair. If head hair is not available, certain body hair can be used as an alternative.

Will the test results from a hair test really reflect drug use over the past 90 days?
Yes. Hair follicles underneath the scalp are surrounded by a dense network of capillary blood vessels. Drugs in the bloodstream are able to incorporate and bind to the hair follicles underneath the scalp. It takes approximately 5 to 10 days for hair containing drug to reach the outer environment on top of the scalp to be collected based on the average rate of head hair growth. Head hair grows approximately 1.3 cm or a ½ inch per month. The standard length of hair tested by the laboratory is the first 3.9 cm or 1½ inches from the root end. Therefore, a hair analysis of 3.9 cm covers a time span of approximately 90 days and detects a pattern of drug use over this timeframe. Many employers find it useful to test both hair and urine (or oral fluid) for pre-employment purposes. Urine (or oral fluid) is useful for detecting recent or new drug use (the last one to three days) and hair for providing an approximate three-month drug history of repetitive use.

What drug testing situations are best suited to a hair test?
Unlike urine drug testing, which may only detect drug use within the past two to three days, hair testing is able to detect a pattern of repetitive drug use for up to 90 days. While urine testing is well suited to detect recent drug use, a hair test is the most effective way to evaluate long-term patterns of repetitive drug use, making it an excellent option for pre-employment or random testing programs.

View a recording of our webinar, Hair Testing 101: Combing Through the Science.

For more information about drug testing, visit our website or contact us online.