A biotin-avidin based screening test for methamphetamine in urine

A biotin-avidin based screening test for methamphetamine in urine samples has been developed. The assay method utilizes the immunoprecipitin reaction between an antibody to methamphetamine and a conjugate prepared by complexing avidin with a biotinyl amphetamine derivative. The rates of the immunoprecipitin reaction is monitored on the Beckman ARRAY 360 nephelometer. Methamphetamine inhibits the precipitin reaction, and the extent of inhibition allows the quantitation of methamphetamine in the urine samples. Using a cut-off value of 0.7 microgram ml-1, the assay correctly predicted 83 of 84 samples (98.8%) confirmed to be positive by GC-MS (> 500 ng ml-1). Of 59 GC-MS confirmed negative samples, 46 samples were found to be negative by this method as compared to 34 samples determined with the EMIT assay. Within-run and between-run relative standard deviations near the cut-off value were less than 4%. Cross-reactivity with amphetamine was < 7%.