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Published:
Journal of Analytical Toxicology,
ISSN 0146-4760,
Volume 24,
Number 8, November/December, pp. 726-732
New Fluorescence
Polarization Immunoassays for Analysis of Barbiturates and Benzodiazepines in
Serum and Urine: Performance Characteristics
K.S. Schwenzer,
R. Pearlman, M. Tsilimidos, and S.J. Salamone*
Roche Diagnostic Systems, Somerville, New Jersey 08876
R.C. Cannon, S.H.Y. Wong, S.B. Gock, and J.J. Jentzen
Office of the Milwaukee County Medical Examiner and the Department of Pathology,
Medical College of Wisconsin, Milwaukee, Wisconsin 53226
The performance of the new fluorescence polarization immunoassay reagents Cassette
COBAS® INTEGRA Serum Benzodiazepines assay (SBENZ) and Cassette Serum Barbiturates
assay (SBARB) was evaluated as compared to other immunoassays (Abbott TDx®
Serum Benzodiazepines, Abbott TDx Urine Benzodiazepines, Behring EMIT® Serum
Benzodiazepines, Abbott ADx® Serum Barbiturates, Behring EMIT Serum Barbiturates,
and the COBAS INTEGRA Barbiturates (BARB) urine assay) and gas chromatography–mass
spectrometry (GC–MS). Recoveries of nordiazepam and secobarbital using
the SBENZ and SBARB assays, respectively, were equivalent for serum, plasma,
and urine. Cross-reactivities of structurally related benzodiazepines, barbiturates,
and their metabolites were very similar in serum and urine for the SBENZ and
SBARB assays. Precision was within 5.4% for SBENZ serum and within 11% from
10 to 100 ng/mL for urine. Precision was within 5% for SBARB serum and within
7% from 136 to 277 ng/mL for the urine application. The standard curves for
SBENZ and SBARB were stable for at least 16 weeks with the reagents stored open
on the COBAS INTEGRA analyzer. Clinical comparison of the SBENZ serum assay
indicated an increased pickup rate, as confirmed by GC–MS, compared to
TDx and EMIT. The diagnostic sensitivities of the SBENZ serum application, TDx,
and EMIT versus GC–MS were 100%, 89%, and 36%, respectively. The diagnostic
specificities were 71%, 79%, and 100%, respectively. The diagnostic sensitivities
of the SBENZ urine application and TDx versus GC–MS were 100% and the diagnostic
specificities were 88%. The increased positive pick-up of the SBENZ assay compared
to the other immunoassays is most probably due to the difference in the limit
of detection (LOD) and the increased cross-reactivity for the low-dose benzodiazepines.
Clinical comparison of the SBARB serum assay indicated an increased positive
pick-up rate, as confirmed by GC–MS. The diagnostic sensitivities of the
SBARB serum application, ADx, and EMIT versus GC–MS were 96%, 65%, and
35%, respectively. The diagnostic specificities were all 100%. The diagnostic
sensitivities for the SBARB urine application and BARB versus GC–MS were
all 100%, and the diagnostic specificities were all 91%. The SBENZ and SBARB
kits demonstrated increased sensitivity for the detection of benzodiazepines
and barbiturates in both serum and urine compared to the other immunoassays. Reproduction
of editorial content of this journal is prohibited without publisher’s
permission.
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