Detection of Drugs in Nails: Three Year Experience

Nails (fingernails and toenails) are made of keratin. As the nail grows, substances incorporate into the keratin fibers where they can be detected 3-6 months after use. Samples are collected by clipping of 2-3 mm of nail from all fingers (100 mg). We present drug testing results from 10,349 nail samples collected from high-risk cases during a 3-year period of time. Samples were analyzed by validated analytical methods. The initial testing was performed mostly using enzyme-linked immunosorbent assay, but by liquid chromatography-tandem mass spectrometry (LC-MS-MS) as well. Presumptive positive samples were subjected to confirmatory testing with sample preparation procedures including washing, pulverizing, digestion and extraction optimized for each drug class. The total of 7,799 samples was analyzed for amphetamines. The concentrations ranged from 40 to 572,865 pg/mg (median, 100-3,687) for all amphetamine analytes. Amphetamine and methamphetamine were present in 14% of the samples, 22 samples were positive for 3,4-methylenedioxymethamphetamine (0.3%), 7 for methylenedioxyamphetamine (0.09%) and 4 for 3,4-methylenedioxy-N-ethylamphetamine (0.05%). Cocaine and related analytes were found in 5% samples (7,787 total), and the concentration range was 20-265,063 pg/mg (median 84-1,768). Opioids overall ranged from 40 to 118,229 pg/mg (median 123-830). The most prevalent opioid was oxycodone (15.1%) and hydrocodone (11.4%) compared with 1.0-3.6% for the others, including morphine, codeine, hydromorphone, methadone, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine and oxymorphone. Carboxy-Δ-9-tetrahydrocannabinol positivity rate was 18.1% (0.04-262 pg/mg, median 6.41). Out of 3,039 samples, 756 were positive (24.9%) for ethyl glucuronide (20-3,754 pg/mg, median 88). Other drugs found in nails included barbiturates, benzodiazepines, ketamine, meperidine, tramadol, zolpidem, propoxyphene, naltrexone and buprenorphine. Nail analyses have become a reliable way of determining the long-term use and abuse of drugs. Extraction techniques are simple and produce accurate and precise results. Sensitive analytical instrumentation, mainly LC-MS-MS, allows for detection of femtogram (10(-15) g) quantities of substances in nails. Samples were from a high-risk population, therefore the extraordinary positivity rate was observed.