A biotin-avidin based screening test for methamphetamine in urine

Abstract

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 rate 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 μg 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%.