SOFT - TIAFT 1998 Poster Session 1 Wednesday October 7, 1998

Jennifer R. Simer, Keith W. Kardos, Todd K. Chuss, R. Sam Niedbala

STC Technologies, Inc., 1745 Eaton Avenue, Bethlehem, PA 18018, USA

The traditional testing for determination of methamphetamine use has been through the collection and analysis of urine or blood plasma. Due to the invasiveness and potential violation of privacy for the donor with current techniques, oral fluid collection and testing has been investigated as an alternative method for the determination of methamphetamine use. One disadvantage of oral fluid is that the drug concentration is generally lower than what is found in urine.

The object of this study was to evaluate the STC Methamphetamine MICRO-PLATE EIA for oral fluid collected using the OraSure® Oral Specimen Collection Device and compare it to the STC Methamphetamine MICRO-PLATE EIA for urine. The analytical sensitivity was evaluated by determining the LOD (Limit of Detection), which is defined as the average signal-noise ratio of the 0 ng/mL concentration (A0) minus the noise times three (LOD = A0 - 3SD). The oral fluid EIA LOD is 1.0 ng/mL, and the urine EIA LOD is 50 ng/mL. A study on the effects of sample pH determined that an oral fluid pH of 3, 4, or 5 caused false positives at a 10 ng/mL cutoff, but in the urine no effect of pH was found. Cross-reactivity studies involved 48 ubiquitous cross-reactants (10,000 ng/mL concentration), none of which produced a positive result in both assay formats, and 16 analogous cross-reactants. The following data for analogous cross-reactants is expressed in % cross-reactivity (oral fluid/urine, nd = not detected): L-methamphetamine (145/262), MDMA (358/827), MDA (1.1/3.4), B-phenethylamine (nd/0.22), D-amphetamine (nd/0.55), diphenhydramine (0.009/0.15), fenfluramine (5.7/1.0), isoxsuprine (nd/1.5), L-ephedrine (0.97/0.99), L-phenylalanine (nd/0.78), mephentermine (1.3/0.37), phentermine (0.07/0.1), phenylephrine (0.1/0.28), phenylpropanolamine (nd/0.19), procaine (0.07/0.16), and pseudoephedrine (1.3/1.5). The precision studies using 0, 5, 10, and 20 ng/mL oral fluid calibrators indicate intra-assay % CV of 8.3, 11.8, 10.5, and 11.4, and inter-assay % CV 4.2, 6.7, 10.6, and 8.1, respectively.

Eighty-one (81) matching saliva and urine clinical specimens (57 from self-reported, methamphetamine users and 24 from non-users) were tested with EIA and GC/MS (LOQ = 1 ng/mL). Thirty-nine (39) oral fluid specimens and 41 urine specimens were negative by GC/MS using a 10 ng/mL cutoff for oral fluid and a 500 ng/mL cutoff for urine. The oral fluid EIA detected 39 true negatives and 42 true positives; therefore, the percent sensitivity and specificity for the EIA oral fluid versus GC/MS were determined to be 100% and 100%, respectively.

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