SOFT 2004 Meeting Abstracts - Society of Forensic Toxicologists
SOFT 2004 Meeting Abstracts - Society of Forensic Toxicologists
SOFT 2004 Meeting Abstracts - Society of Forensic Toxicologists
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
A57 <br />
ELISA FOR THE SCREENING OF OPIA TES, BENZODIAZEPINES, CANNABINOIDS,<br />
METHAMPHETAMINE, AND COCAINE METABOLITE IN POSTMORTEM FORENSIC<br />
WHOLE BLOOD<br />
Paul J. Jannetto', 1,2, Elvan Laleli-Sahin,,2, Susan Gock', Steven H. Wong"2, and Jeffrey Jentzen l , 2<br />
'Milwaukee County Medical Examiner's Office; 2Department <strong>of</strong> Pathology, Medical College <strong>of</strong> Wisconsin<br />
In both forensic and clinical toxicology, enzyme-linked immunosorbent assay (ELISA) based screening<br />
methods are becoming increasingly popular and replacing radioimmunoassay (RIA) methods for numerous<br />
reasons including: cost, automation, ease <strong>of</strong> use, and disposal issues. Currently, the Milwaukee County<br />
Medical Examiner's Office uses the Immunalysis RIA kits to screen whole blood specimens for common<br />
classes <strong>of</strong> drugs such as opiates, benzodiazepines, cannabinoids, methamphetamine, and cocaine<br />
metabolite. In this study, the assay performance <strong>of</strong> the RIA kits was compared to the ELISA kits from the<br />
same manufacturer using fifty-one forensic samples. To further validate the ELISA-based assays, the intraand<br />
interday precision, cross-reactivity, and dose-response curves were analyzed for opiates,<br />
benzodiazepines, cannabinoids, methamphetamine and cocaine metabolite to determine if the ELISA kits<br />
were an acceptable alternative to the RIA kits.<br />
Of the fifty-one samples screened by both RIA and ELISA for opiates, benzodiazepines, cannabinoids<br />
(THC), methamphetamine and cocaine metabolite, there were a total <strong>of</strong> five discordant results (3 THC, and<br />
2 methamphetamine). Gas chromatography-mass spectrometry analysis indicated five unconfirmed positive<br />
results (false-positives) by RIA (3 cases for THC and 2 cases for methamphetamine). On the other hand,<br />
the ELISA kits had a 100% positive and negative predictive value for all five assays. The intraday<br />
coefficient <strong>of</strong>variation (CVs; n == 10) near the immunoassay cut<strong>of</strong>f concentration (60 ng/mL) was 4.0-7.7%<br />
for all five assays, while the interday CVs (n 5) at the immunoassay cut<strong>of</strong>f concentration (50 ng/mL) was<br />
8.4-10.7%.<br />
Overall, a comparative assessment <strong>of</strong> common drug screening assays by RIA and ELISA from the same<br />
manufacturer indicated some differences in analytical performance. The ELISA based screening kits<br />
<strong>of</strong>fered acceptable precision, superior specificity/sensitivity and was an economical alternative to the RIA<br />
kits. The ELISA-based assays are particularly attractive for forensic specimens for several reasons<br />
including: the ability to use a variety <strong>of</strong>sample matrices (e.g. whole blood), small sample volumes reducing<br />
interferences from some forensic matrices, a long shelf life, and the ability to incorporate automation and<br />
increase throughput. Based on these criteria, the Milwaukee County Medical Examiner's Office has<br />
adopted the ELISA-based assays to screen forensic samples for drugs <strong>of</strong> abuse. All presumptive positive<br />
immunoassay results are then confirmed by GCIMS.<br />
Key words: ELISA, RIA, Method validation<br />
Page 171
Change language