SOFT - TIAFT 1998 Poster Session 2 Wednesday October 7, 1998

Stuart C. Bogema

Forensic Testing, Inc. P.O. Box 196, Clifton, VA 20124, USA

Workplace drug testing in the US typically includes screening for amphetamines: amphetamine (A) and methamphetamine (M). US DHHS and DOT regulations specify initial screening for amphetamine at a cutoff of 1,000 ng/mL. Immunoassay manufacturers have utilized A-specific antibodies, M-specific antibodies, a combination of both and less specific antibodies as they attempt to optimize A and M detection while minimizing false positive screens due to cross-reacting substances. Immunoassays used in laboratories, such as Date Behring Syva EMIT II and Roche Diagnostics Systems OnLine, are designed to detect both A and M. Non-instrumental immunoassays designed for on-site drug testing use antibodies that are more specific and more specific for either A or M. The purpose of this study was to compare A and M detection by EMIT II, OnLine, the M-specific Princeton BioMeditech AcuSign-5 and the A-specific Roche Diagnostics Systems TesTcup-5 in a random set of specimens.

Urine specimens that tested positive for amphetamines using the Dade Behring Syva EMIT II monoclonal immunoassay using a 1,000 ng/mL cutoff were used in the study. Fifty (50) specimens were provided by PoisonLab, Inc. (PL, San Diego, CA) and fifty-three specimens were provided by American Medical Laboratories, Inc. (AML, Chantilly, VA). All specimens were quantified for A and M by GC/MS at the two labs. Of the 103 specimens, 28 or 27% were negative for both A and M. 25 had only A above the GC/MS cutoff of 500 ng/mL, 6 had only M above the 500 ng/mL GC/MS cutoff and 44 had both A and M above 500 ng/mL. Specimens from PL were mostly A and M, while specimens from AML contained mostly A alone. This, M predominated in the West Coast lab and A predominated in the East Coast lab. 26 of 28 false positives by EMIT II came from AML. OnLine had four false positives (3.9% of 103 specimens) and one false negative that contained 580 ng/mL of A. The M-specific AcuSign-5 had 5 (4.9%) false positives and 28 false negatives (37.3% of 75 true positives). The A-specific TesTcup had one (1.0%) false positive and 12 false negatives (16.0%) of 75 true positives). For detection of amphetamines overall, the A-specific TesTcup detected 84% of the true positives compared to 62.7% for the M-specific AcuSign-5. OnLine had much fewer false positives than EMIT II, 3.9% versus 27.2%.

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