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

Paul J. Orsulak, Linda C. Akers and Neal Bellet*

Toxicology Laboratories, VA North Texas Health Care System, Dallas, TX 75216, USA
Roche Diagnostics/Boehringer Mannheim Corporation, Pleasanton, CA 94566, USA

Methadone, a synthetic diphenylheptane-derivative opiate agonist, is primarily used as a substitute for heroin and other opiates during withdrawal to eliminate symptoms and to temporarily maintain chronic relapsing heroin addicts. Screening methadone is an important clinical tool for evaluating compliance. However, a small subset of patients metabolize methadone to 2-ethylidene-1,5-dimethyl3,3-diphenylpyrrolidine (EDDP) so quickly that they appear negative upon conventional methadone immunoassay screening. The purpose of this study was to evaluate the performance of the new CEDIA® DAU assay for EDDP. Assay performance was assessed as part of a multi-center clinical evaluation of EDDP utility as a screening tool. The evaluation included three Boehringer Mannheim Corporation Hitachi Model 717 analyzers, one Hitachi Model 747 analyzer and one Hitachi Model 917 analyzer.

Within-assay reproducibility over the five analyzers range from 2.1 to 5% at a mean EDDP concentration of 75.5 ng/mL, and 2.4 to 4.7% at a mean concentration of 128.8 ng/mL. Between assay reproducibility was assessed on one Hitachi 717 analyzer, the Hitachi 747 analyzer and the Hitachi 917 analyzer. Coefficients of variation over a 14 day period (n = 30) were from 3.8 to 6.3% at 72.3 ng/mL and 3.5 to 4.5% at 126.9 ng/mL. Cross-reactivity to methadone was tested and was <0.02%. Method comparisons gave correlation coefficients of 0.981 (n = 80) compared to GC/MS and 0.964 compared to HPLC (n = 79).

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