A hair follicle test provides insights into an individual’s substance use history. It detects drug compounds and their metabolites incorporated into hair strands as hair grows. Unlike other drug tests, hair testing offers a longer detection window, typically covering up to 90 days of past substance exposure. This makes it a useful tool for employment screening, legal contexts, and rehabilitation monitoring.
Key Elements of a Hair Follicle Test Report
A typical hair follicle test report begins with identification details for the individual (name, unique ID). It also includes laboratory information (name, contact), and dates of sample collection and report generation. These details ensure proper record-keeping and traceability.
The report details tested substances, often common drug classes like amphetamines, cocaine, opioids, cannabis, and phencyclidine (PCP). For each substance, the report indicates detection and concentration, typically measured in picograms per milligram (pg/mg) or nanograms per milligram (ng/mg) of hair.
An important aspect of the report is the inclusion of cut-off levels. These are specific thresholds that determine whether a detected substance concentration is considered positive. Laboratories often use two sets of cut-off levels: one for initial screening tests, and a lower one for confirmatory tests, which are more precise. The report also specifies the detection window, generally 90 days for scalp hair (1.5 inches). Any disclaimers or notes from the laboratory regarding the sample or testing process may also be present.
Interpreting Test Outcomes
Understanding the results of a hair follicle test involves distinguishing between negative, positive, and inconclusive findings. A negative result means that no drugs or drug metabolites were detected in the hair sample above established cut-off levels. This indicates the individual did not consume the tested substance within the detection window, or the amount consumed was below the threshold for detection.
A positive result signifies that a drug or its metabolite was detected in the hair sample at a concentration equal to or exceeding the laboratory’s defined cut-off level. When an initial screening test yields a positive result, the sample undergoes a more specific confirmatory test, such as gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-mass spectrometry (LC-MS/MS), to verify the finding and identify the specific substances present. These confirmatory methods help minimize false positives.
An inconclusive or invalid result can occur if there are issues during the testing process, such as insufficient sample quantity, contamination, or technical errors. In such cases, the laboratory cannot definitively determine the presence or absence of substances. An inconclusive result means that the test needs to be re-administered or a new sample collected to obtain a clear outcome.
Factors Influencing Test Accuracy
Several factors can influence the accuracy and interpretation of hair follicle test results. Environmental contamination, where drugs from external sources (e.g., secondhand smoke or handling) contact hair, can potentially affect test outcomes. While laboratories typically wash hair samples to remove surface contaminants, some drug residue might remain, potentially leading to a positive result even without ingestion. Researchers are developing methods to differentiate between environmental exposure and actual consumption by looking for specific drug metabolites formed within the body.
Hair treatments, such as bleaching, dyeing, perming, or relaxing, can impact drug concentrations in hair. The chemicals used in these processes can damage the hair shaft, which may reduce the detectability of drug metabolites. Studies have shown cosmetic treatments can decrease drug content in hair, with bleaching potentially causing greater reductions than dyeing, although they typically do not eliminate drugs entirely.
Hair color can also play a role, as some studies suggest that drugs like cocaine, methamphetamine, and opioids may bind more readily to melanin, the pigment in darker hair. This could lead to higher detected concentrations in individuals with darker hair, even with comparable drug exposure. The sufficiency and integrity of the collected sample are paramount; an inadequate or improperly collected sample can lead to inconclusive results, underscoring the importance of proper collection procedures.