affected by age (slower growth in older per- sons), disease state, and even weather (finger- nails may grow slower in colder weather).3,6 Some drugs may wash out of fingernails as quickly as three months aſter use; yet, other drugs can have a much longer retention time. Despite this variability, research has shown that the window of detection for drug use in fingernails is at least equivalent to that of hair, and for many drugs the look-back is much longer than for hair.3 Te same drugs that can be detected
in hair samples can also be detected in fingernails. In some cases, fingernails may capture more of a drug than is typically found in hair samples. For example, a 2013 study found that fingernail samples positive for carboxy-THC (a marijuana metabolite) captured five times more of the biomarker than positive hair samples.7
Fingernails
are able to remove the variation in results caused by hair pigment for some drugs. For instance, the same dose of amphetamine may give a 30-fold difference in the amount detected in blonde hair versus black hair. Tis is due to variation in test results for some drugs caused by differences in hair pigment. Fingernail testing removes this variation. Research comparing fingernails and hair for other drugs has shown the two sample types to be equivalent, although the comparison has not been made for all potential substances of abuse. Tese vari- ous studies suggest that fingernail testing is a suitable, and in some cases superior, alternative to hair testing. If a donor’s fingernails are not of sufficient
length, waiting 7–10 days will allow enough fingernail growth to give the ideal sample size. Because a donor’s drug and alcohol use impacts the entire length and width of the fingernail, this new growth will still capture a 3–6 month history of drug use. In contrast, a three-month window of detection in hair can only be achieved if the donor already has at least 1.5 inches of hair on the head. Any new hair growth will not contain any history of previous drug or alcohol use.
www.datia.org
Alcohol Testing in Fingernails Alcohol testing in fingernails, as in hair, is done through the analysis of ethyl glucuro- nide (EtG), a direct alcohol biomarker. EtG is known as a direct biomarker, because it is only produced by the body when ethanol is present. Tis is in contrast to indirect biomarkers such as aspartate aminotrans- ferase (AST), gamma glutamyl transferase (GGT), or carbohydrate deficient transfer- rin (CDT), among others. Indirect markers measure the effects of ethanol consump- tion on the health of the body. Other con- ditions may confound indirect biomarkers, such as age or certain diseases. Ethanol is converted to EtG in the liver and then deposited in fingernails primarily from the nail bed capillaries. Te use of fingernail samples for EtG
testing may be a preferred sample type over hair for two reasons. First, EtG accumulates at higher concentrations in fingernail sam- ples. EtG testing in fingernails eliminates a possible bias seen in hair EtG testing as well. A 2012 study compared EtG levels in paired fingernail and hair samples taken from 606 college students. EtG levels in positive fingernail samples were 2.5 times higher than those detected in positive hair samples.8 Te college student data also suggested
a possible bias for EtG testing in hair sam- ples; fingernail and hair samples taken from male subjects showed strong agreement in their positivity rate. However, there was very litle agreement between the two sample types for female subjects. Earlier research from 2010 demonstrated that EtG in hair could be broken down as a result of some cosmetic hair treatments, such as hair bleaching and dyeing, which may account for the difference between the two sample groups9
(Figure 2 and 3).
Sample Collection Fingernail testing offers several advan- tages in sample collection. Fingernail
Figure 1. Cutaway view of the growing nail.
samples are clipped from the leading edge of the growing nail and are the least intrusive of any testing sample. Fingernails can be collected by the donor themselves in front of a trained observer, as opposed to hair samples which need to be taken by a trained collector. Addition- ally, the collection of fingernails has very low impact on the personal appearance of the donor, which is not always true when hair samples are collected. Fingernails are almost universally available, which may not be true for donors experiencing hair loss and thinning. An ideal sample size for screening and
confirmation of positive results is 100 mg of fingernails. A 2–3 mm clipping—about the width of the edge of a U.S. Quarter— from all ten fingernails will give the optimal sample size.
Conclusion Substance abuse in the 21st
century is
complicated. Detection methods must be open to alternative samples to keep up. Fingernails offer a drug and alcohol testing sample that is a useful, and in many ways superior alternative to hair testing. The rate of growth of fingernails, coupled with the stability of drugs in the nail keratin matrix, provides the longest
datia focus 29
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64