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Published:
Journal of Analytical Toxicology,
ISSN 0146-4760,
Volume 26, Number 7, October 2002,
pp. 513-518
Choice of an ELISA Assay for Screening Postmortem Blood
for Amphetamine and/or Methamphetamine
Tom Kupiec[1], Lacinda DeCicco[1], Vina Spiehler[2],
Gary Sneed[3], and Philip Kemp[3]
[1]Analytical Research Laboratories, Oklahoma City, Oklahoma
[2]Spiehler & Associates, Newport Beach, California
[3]Office of
the Medical Examiner, Oklahoma City, Oklahoma
The object of this study was
to evaluate the suitability of the Neogen Corp. microtiter plate enzyme-linked
immunoassays (ELISA) for the screening of postmortem blood for amphetamine and
methamphetamine and to choose the more appropriate assay for screening. Forty-seven
postmortem whole blood specimens were obtained from drug-involved deaths, which
had been screened and confirmed positive for methamphetamine and/or amphetamine.
Eighty-five negative specimens were obtained from non-amphetamines-involved
deaths, 17 of which involved decomposition. Specimens were tested using the
Neogen Amphetamine Ultra and Neogen Methamphetamine/MDMA microtiter plate ELISA
assays. No matrix effects were found for whole blood in these assays, and a
dilution of 1:5 was chosen to facilitate pipetting and to bring the IC50 of
the microtiter plate ELISA assay within the range of amphetamines concentrations
encountered in medical examiner specimens. True positives, true negatives, false
positives, and false negatives were determined relative to gas chromatography–mass
spectrometry (GC–MS) and graphed for the ELISA. From these graphs and
the receiver operating curves (ROC), the optimal cut-off for the Neogen Methamphetamine/MDMA
ELISA was 50 ng/mL methamphetamine equivalents and the optimum cut-off for the
Neogen Amphetamine Ultra ELISA was 100 ng/mL amphetamine equivalents. The Neogen
Methamphetamine ELISA had a sensitivity of 93.6% ± 3.5% and a specificity
of 77.6% ± 4.5% versus GC–MS at the cut-off of 50-ng/mL methamphetamine
equivalents. The Neogen Amphetamine Ultra ELISA had a sensitivity of 95.7% ±
3.0% and a specificity of 72.9% ± 5.2% versus GC–MS at the 100-ng/mL
amphetamine equivalents cut-off. The areas under the ROCs were equivalent for
the two ELISA assays. Reproduction
of editorial content of this journal is prohibited without publisher’s
permission.
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