Amphetamines in hair by enzyme-linked immunosorbent assay.
Human hair was collected from the occipital crown region of the head from several subjects; these hair samples were presumptively positive for amphetamines by a previously evaluated immunoassay. Hair was washed briefly with methanol to remove external contamination, then extracted with hot methanol for 2 h to recover the drugs. The extracts were evaporated to dryness, reconstituted in buffer, and analyzed using a new enzyme-linked immunosorbent assay (ELISA) technique adapted for the detection of amphetamines in hair. Gas chromatography-mass spectrometry was used as the reference technique. Cross-reactivity of several related compounds was evaluated by equating the inverse of the ligand concentration at 50% antibody binding to the affinity constant for each compound. The ratio of a compound's affinity constant to that for d-methamphetamine was used to derive percent crossreactivity. These experiments yielded values of 30.8% for d-amphetamine, 7.4% for I-methamphetamine, 4.3% for phentermine, 2.9% for I-amphetamine, and <1% for ephedrine, methylenedioxyamphetamine, and methylenedioxymethamphetamine. Cross-reactivity of unrelated compounds was found to be non-existent. The optimum cutoff concentration was determined by receiver operating characteristic curve analysis to be 300 pg/mg and the observed limit of detection was 60 pg/mg. Intra-assay precision at 300 pg/mg was 3.3% (coefficient of variation, CV), and the interassay CV was 10.5%. The sensitivity and specificity of the method were 83% and 92%, respectively.
Sweeney
S A
SA
Associated Pathologists Laboratories, Las Vegas, Nevada 89119, USA.
Kelly
R C
RC
Bourland
J A
JA
Johnson
T
T
Brown
W C
WC
Lee
H
H
Lewis
E
E
D019969:Amphetamine-Related Disorders / Q000175:diagnosis*; D000915:Antibody Affinity / Q000276:immunology; D003429:Cross Reactions; D004797:Enzyme-Linked Immunosorbent Assay; D008401:Gas Chromatography-Mass Spectrometry; D006197:Hair / Q000737:chemistry*; D006801:Humans; D008694:Methamphetamine / Q000032:analysis* / Q000276:immunology; D012372:ROC Curve; D012680:Sensitivity and Specificity; D015813:Substance Abuse Detection / Q000379:methods*
D008694:Methamphetamine