TRENDS IN
DRUG USE BY JOSEPH SALERNO, UNITED STATES DRUG TESTING LABORATORIES, INC. (USDTL)
Nailing Drug and Alcohol Testing: The Use of Fingernails as an Alternative to Hair Testing
Fingernail testing has many similarities to hair testing, as well as some advantages including ease of collection, stability, and a longer window of detection.
S ubstance abuse in the 21st century is
an ever-evolving and sophisticated animal. Trough the Internet, new
drugs—both illicit and prescription—are available in dizzying arrays. Along with the new drugs being abused are new methods to avoid detection. Labs must maintain constant research and development to meet the needs of the ever-changing market. Tankfully, the old adage ‘you are what you eat’ still rings true. Hair testing has caught on as a popular
sample to detect substances of abuse and so has the ability of the abuser to Google ways to offset drug tests. In an effort to remain ahead of the curve in this complex market, researchers have turned to other sample types to go beyond the limits of hair testing. Fingernails are composed of keratin, the same protein matrix found in hair. Fingernail testing has many similarities to hair testing, as well as some advantages including ease of collection, stability, and a longer window of detection. Te detection of substances in fingernails provides a powerful tool for the drug and alcohol testing industry.
Incorporation of Drug and Alcohol Biomarkers in Nail Samples Fingernail keratin is four times thicker than that found in hair. While hair grows only in length from the hair root, nail keratin grows in two directions. From the germinal matrix, fingernails grow in length as they emerge from the nail root. As they elongate, fingernails also grow in thickness with new keratin being added to the underside of the fingernail along the nail bed (Figure 1). It was previously thought that substanc-
es could only enter the fingernail from the germinal matrix, but research on thera-
28 datia focus
peutic drug monitoring has debunked this model of drug capture.3,4
Blood vessels
in the nail bed continuously feed the growing fingernail. As a result, drug and alcohol biomarkers are trapped in the keratin matrix over the entire fingernail as it grows in length. Fingernails are a reservoir matrix made
up of a tight weave of keratin fibers that are also porous. This tight but porous nature means that nails are a superb ma- trix for catching and trapping drug and alcohol biomarkers.5
Chronic drug or
alcohol use causes a continuous build-up of biomarkers along the entire fingernail as it grows.
Detecting Drugs in Fingernails Amphetamine and methamphetamine were the first illicit substances to be detected in nail samples in 1984.1
Te role
of nails in other uses like environmental exposure analysis, forensics, poison inves- tigation, and others extends as far back as the 1800s.2
Much of what is known about
the drugs in fingernails comes from drug therapy monitoring, most notably early studies into the antifungal treatment of toenails.3
Despite gaining acceptance as
a tool for alcohol and substance abuse detection in recent decades, the body of evidence supporting fingernail testing spans nearly two centuries. Drug and alcohol use can be detected in
fingernail samples 1–2 weeks following use. In that time, the leading edge of the fingernail can grow out to a length that gives sufficient quantity for testing. Te window of detection for drugs in fingernails is from three months up to six months aſter use, depending on several factors. Te rate of fingernail growth can vary from person to person and can be
summer 2014
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