SOFT 2004 Meeting Abstracts - Society of Forensic Toxicologists

F20
CONFIRMATION RATES OF INITIAL DRUG ASSAYS IN A GROUP OF HHS-CERTIFIED
LABORATORIES, JANUARY 01 THROUGH DECEMBER 31, 2003
II: NON-REGULATED SPECIMENS
Craig A. Sutheimer l *, Michael R. Baylor I, John Irvingl, John M. Mitchell\ Donna M. Bush 2 : IRTI
International, Research Triangle Park, NC, USA; 2DWP, SAMHSA, Rockville, MD, USA
The specificity of immunoassays associated with urine drug testing has long been a subject of discussion among
forensic toxicologists. While it has been known that some drug class immunoassays have very high rates for the
confirmation of presumptive positives, it is also recognized that other drug class immunoassays produce a
significant number of presumptive positives that fail to confirm when subjected to confirmatory testing by
GCJMS. These observations are further confounded as initial and confirmatory drug test cutoff concentrations
change and as the number of drug analytes in confirmatory panels are broadened. These observations led to an
examination of the immunoassays currently in use at drug testing laboratories. The goal of this study was to
document the possible differences in specificities and cross-reactivities of the technologies with multiple cutoffs
in both the initial and confirmation testing procedures in addition to possible variability in the analytes defined in
the confirmatory panels.
The study included data from 10 laboratories certified by the U. S. Department of Health and Human Services
(HHS) encompassing over 10 million specimens tested during 2003. These specimens were not subject to the
criteria of the Mandatory Guidelines for Federal Workplace Drug Testing Programs. The data was obtained from
laboratories that used CEDI A, EIA and KIMS technologies as a primary initial test, with varying initial and
confirmatory test cutoffs. Some laboratories conducted additional screening of presumptive positives with a
second initial test. Summaries of specimen testing and confirmation rates are presented in the tables below. The
confirmation rates are expressed as percent of the presumptive positives confirmed by GC/MS for each drug
class. The lowest and highest confirmation rate for each "initial/confirmatory testing cutoff pair" identified is
provided.
Amohetamines BZE
Specimens Tested 10 142,363 10,136424
Presumptive Positives 101,653 97,891
Confirmed Positives I 57,283
96,283
Opiates PCP
10,117,626 10 006,492
103,081 5,838
36,821 3,389
I
THC-COOH
10,188,976 i
347,905 I
326,039 1
T Barbs I Benzos Methadone MQL Propoxyphene
. Specimens Tested T 4,585,890 I 4,271,398 3,943430 2,504,097 3,852,794
Presumptive Positives I 15,281 47,639 10,305 56 28,188
Confirmed Positives T 13,729 L 28,260 9,248 4 26,045
I Initial Test Assay
: Confirmation Rates
Amphetamines BZE Opiates PCP I THC-COOH
i Lowest Rate 3.4% 80.5% 25.0% 59.0% I 60.8%
I Highest Rate 97.2% 99.3% 71.8% 96.4% l 100.0%
I
Initial Test Assay Barbs Benzos Methadone MQL ! Propoxyphene
I Confirmation Rates
-
i Lowest Rate 76.1% 45.9% 69.8% NA 22.7%
I
I Highest Rate i 100.0% 83.7% 100.0% 8.3% 100.0~
This study evaluated the presumptive positive rates and the confirmation rates for primary initial tests by
immunoassay method. The results w~re examined with consideration of assay cross-reactivity and specificity.
As expected, some assays and technologies appear to better identifY specimens containing analytes of interest
above the defined cutoffs. While the study assesses current capabilities of existing technologies from a large
population of "real" specimens, it also provides information that may be useful in formulating future guidelines
by which newer technologies, additional drug classes and additional analytes may be evaluated.
Keywords: non-Regulated testing, HHS-certified laboratories, Immunoassay confirmation rates, Calendar Year
2003
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