Stories that hair can tell.

Sir,

Studying the characteristics of hair samples is an invaluable method in assessing a variety of factors such as drug/alcohol intake, hormono-metabolic indices, etc. The noninvasive sample collection, under close supervision, the reflection of a matching timeline in case of claims or suspicion of a break in the chain of custody, the increased window of detection for the drugs make hair sampling an excellent means of diagnosis. I attempt to review the literature regarding the role of hair testing as a complementary method in clinical and forensic toxicology and workplace drug testing.

The incorporation of methamphetamine (MA) into human hair was studied using matrix-assisted laser desorption/ionization (MALDI), time-of-flight (TOF), and MALDI-Fourier transform ion cyclotron resonance (FTICR). A longitudinal section of a lengthwise manually-cut single human hair shaft from a chronic MA user showed a barcode-like image (generated with repeated intakes of MA by monitoring MA-specific product ion) which was confirmed by ultra-high resolution mass spectrometry by FTICR.[1] Similarly the use of ecstasy correlated significantly with the presence of MA in hair samples.

Analyzing head hair morphine concentrations of 42 consecutive cases of fatal heroin overdose, 100 current street heroin users, and 50 drug free clients showed that higher concentrations indicated higher levels of heroin consumption in the 2 months prior to death or interview.[2]

Combining the parameters fatty acid ethyl esters (FAEE) and ethyl glucuronide (EtG) in hair samples strongly increases the accuracy of diagnosing chronically excessive alcohol abuse.[3]

Exposure to secondhand smoke can be measured by analyzing hair nicotine and cotinine. Using liquid chromatographic-tandem mass spectrometric (LC-MS) analysis, a study showed that both nicotine and cotinine could be detected in beard samples (of six male nonsmokers following a single exposure to 4 mg of nicotine) within 24 h of the exposure.[4] Upon evaluation of the effects of maternal smoking on fetal growth, it was found that hair nicotine is a better predictor of reductions in body weight for gestational age than either hair cotinine or self-report.

In a study spanning five legal cases involving the use of benzodiazepines and zolpidem and an animal study on drug incorporation into hair, diazepam and its three metabolites, as well as lorazepam, were detected in hair from both multiple- and single-dose administration.[5]

Instrumental neutron activation analysis (INAA) of hair helps confirm the immediacy of arsenic ingestion in an otherwise ambiguous case of acute versus chronic arsenic poisoning. In organo-phosphate poisoning higher concentrations of dialkyl phosphate metabolites (corresponding to the ingested parent compound) can be detected in the segments proximate to the suicide period.

Hair cortisol levels in pregnancy are shown to reliably measure hypothalamic-pituitary-adrenal axis over an extended period. Increased hair cortisol in the 3 months prior to the event which implies chronic stress may be a contributing factor for acute myocardial infarction.

Apart from circumventing the methodological problems associated with collection of plasma, urine, or saliva, hair sample testing is far reaching in many ways and new paths are being paved for its wide spread use.