The collection of hair to conduct workplace drug testing is not consistent. Each laboratory undergoing hair testing has established protocols for the collection of hair samples. These protocols may be performed on the job site or at another location by a trained collector who is employed by the donor’s employer or an agent that assists their employer with the drug testing program. These agents are referred to as Third Party Administrators (TPA). Generally, head hair is the primary anatomical collection site, but some laboratories will collect at other body hair sites such as the nape of the neck, axillary, or pubic areas. The posterior vertex region of the scalp (crown areas is the most common collection site. It is important that chain-of-custody protocols to document sample handling, be established at the time of collection to ensure the legal defensibility of the hair results test.
Most laboratories require a minimum of 100 to 200 mg of hair (e.g., the size of the end of a shoe lace but no more than a pencil eraser) to allow for multiple testing procedures. Although hair could he plucked, cutting the hair as close to the scalp as possible is the preferred method. The cubing utensil should be thoroughly cleaned between collections. All hairs should be kept in the same orientation noting the root end. Although whole hair strands are collected, laboratories usually use the first 2 to 4 cm closest to the scalp for analysis and discard the rest, representing up to 90 days of drug exposure.