Effective Wash Procedure Critical in Hair Testing

By Jim Dyke, Psychemedics Corporation

Hair analysis for the detection of drug use in workplace testing continues to grow in popularity due to its wider window of detection and ability to detect repeat drug users. However, one aspect that has lacked agreement in the field is how best to ensure that a positive result is due to ingestion rather than environmental exposure.

Hair analysis technology capitalizes on how the body metabolizes ingested drugs as they flow through the bloodstream and deposit in the cortex of the hair. Two important regions in the basic structure of hair are hair analysis: the cuticle and the cortex. The cortex is the region inside the hair shaft fed by blood while the hair is forming in the follicle. The cuticle is the region on the outside of the hair shaft that is affected by the environment. The hair acts like a tape recorder—“recording” the deposits inside the hair in proportion to use over time as drugs are deposited.

To ensure accurate hair testing results, it is important to eliminate the possibility that the results are being influenced by drugs deposited on the outside of the hair from contamination versus drugs deposited on the hair from ingestion. This is critical to provide accurate test results and to prevent false positives.

Wash Procedure Can Answer the Challenge of Contamination

Before analysis, washing the hair samples is a standard laboratory procedure that has been actively studied since the early years of hair analysis research when the need for a wash that addressed the challenges presented by contamination was realized. Fairness and accuracy can be achieved by implementing an effective wash procedure that addresses the challenges of ensuring that the hair test is only analyzing what is inside the hair and resulting from drug use.

Accurately identifying drugs’ ingestion depends on factoring out drugs present from other sources, including environmental contamination and sweat. Environmental contamination can be caused by various factors, including: during the use of the drug, secondhand smoke or being in the vicinity of drug users, or from residues left in an environment by various means. With sweat, ingested drugs can be excreted in perspiration and subsequently deposited on the hair externally. To achieve accurate results, the hair testing laboratory must include in their process the ability to remove and account for any deposits on the external portion of the hair, evaluate if the wash procedure hair test was effective, and then compare that against the cutoff levels.

Normal hair may exhibit the presence of drugs in two different areas:

  • On the Surface of the Hair: Surface contamination such as powder or vapor where the drug has not been exposed to moisture and therefore essentially rests on the surface of the cuticle; this type of contamination can be removed readily by shorter washing methods. However, short wash procedures do not eliminate contamination in the presence of moisture, such as sweat, humidity, or bathing/shampooing that diffuses into the proteins of the cuticle but does not penetrate the cuticle.
  • On the Inside of the Hair: Drugs present inside the cortex of the hair deposited in the follicle during ingestion that grows out into the hair’s shaft above the scalp.

While most hair testing laboratories may wash the hair samples as a standard practice, there are many different types of wash processes that exist, offering a wide range of effectiveness in dealing with contamination.

FBI Validates Effectiveness of Extended Wash Procedure

In a recent landmark study conducted by the Federal Bureau of Investigation[i] (FBI) and later published in the Journal of Analytical Toxicology, a wash process was validated when the study concluded that the extended wash and calculation described in conjunction with the measurement of metabolites would exclude false-positive results from environmental contact. The FBI was looking to establish new reporting criteria and interpretation guidelines for forensic casework. The FBI study’s findings were essential as they validated that this washing procedure in hair testing effectively removed contaminants from samples from people who could be legitimately exposed to drugs in a workplace setting.

Background and Key Points of the FBI Study:

  • FBI conducted its study using the published method to determine whether cocaine users could be reliably distinguished from those exposed to cocaine in their daily work – that is, real-life exposure conditions.
  • FBI visited a well-known lab and conducted a study applying and validating the decontamination and calculation methods used. The FBI publication cited previous studies published by the lab in 1993, 2002, 2004, and 2005.
  • FBI’s conclusion means that by using this particularly extended wash and kinetics calculation method, individuals legitimately exposed to cocaine in their daily work (attorneys prosecuting or defending drug charges, law enforcement officers handling drug evidence, crime laboratory employees, etc.) will not be at risk of being identified as cocaine users.
  • As a result of the study, the FBI has now adopted this non-proprietary wash protocol.

The extended wash procedure, cited by the FBI, was empirically developed over the last 30 years[ii] by studying the washing characteristics of laboratory-contaminated samples and thousands of drug-user samples. These results have been published and shared with the hair testing community since first being developed.

This wash protocol requires multiple steps, including:

  • An extended wash procedure: Six steps with a three hour and 45 minute wash time, changing the wash solution between each step.
  • Analysis of the final wash: An analysis of the last of the six wash solutions to ensure that all contamination has been removed or accounted for.
  • Wash criterion: The amounts of the drug in the last wash relative to that in the washed hair indicate whether the sample has been sufficiently decontaminated and the result accurately reflects the ingested dose. The amount of drug in the last wash is multiplied by 5 to represent 5 more hours of washing, and that number is then subtracted from the amount of drug in the hair.  The outcome of the calculation must be at or above the cutoff to be called “positive,” demonstrating the drug’s ingestion.
  • Metabolite identification: If the wash criterion fails, the metabolites in the hair sample and the last wash are examined (the metabolite ratio in the last wash is often similar to that in the digested hair).
  • Cutoff levels: The minimum measurement applied to drug testing so that only amounts of a drug or its metabolite above a specified level is reported as positive.

There has been further validation of this effective extended wash procedure and wash criterion in numerous other studies, including:

  • A 2011 Department of Justice (DOJ) study demonstrated that this published wash procedure was the only method effective at addressing external contamination and drug use[iii]
  • A 2005 scientific study published in the Journal of Analytical Toxicology demonstrated that the washing method used protected against the erroneous interpretation of contaminated hair[iv]
  • A 1997 Mieczkowski study published in Forensic Science International assessed undercover narcotics officers’ passive contamination and concluded that the wash protocol provided adequate safeguards against confusing contamination with ingestion[v]


Fundamental Wash Available to All Laboratories

The FBI study is critical to all hair testing laboratories. It provides validated proof from a highly-respected third party that the extended wash procedure tested by the FBI effectively removes contaminants from people who could be legitimately exposed to drugs in a workplace setting. The method is published, unpatented, and available to all hair testing labs.

Though the wash protocol identified in the study requires a significant investment in extra time and expense incurred by the testing laboratory, these extensive measures are put in place to protect the individuals taking the test and ensure fair and accurate results.

Effective Wash Protocol Provides Assurance of Results

Without a validated wash procedure, there are no safeguards to ensure that the reported drug results have not been influenced by contamination, and there is no assurance of fair and accurate reporting. Regardless of the nature of an individual’s industry or environment, an effective wash protocol is necessary to assure those drug positives result from actual drug use and not drug exposure.

These developments in the technology of hair testing coincide with recent closed sessions of the Drug Testing Advisory Board of SAMHSA’s CSAP (Center for Substance Abuse Prevention) to discuss hair testing best practices and data, as well as proposed revisions to the Mandatory Guidelines for Federal Workplace Drug Testing Programs[vi]. Accurately identifying drugs’ ingestion is critical in hair testing, and the FBI’s recent validation of the extended wash procedure helps the hair testing industry answer the challenge of contamination.


Jim Dyke is the Corporate Vice President of Sales & Marketing at Psychemedics Corporation, the world’s leading and largest drug testing company using hair analysis. Jim works with organizations in various industries that are mapping out changes to their drug testing programs to balance efficiency and effectiveness.