Single-reagent polarization fluoroimmunoassay for amphetamine in urine

This simple polarization fluoroimmunoassay for detection of amphetamine in urine involves the use of a single reagent: suitably diluted antiserum plus fluorescein-labeled amphetamine as tracer. To this, one adds 10 microL of urine, incubates for a few minutes at room temperature, and measures the fluorescence polarization. By using an antiserum obtained against an immunogen conjugated via the para position of the drug's phenyl ring, we have attained greater specificity than that of most existing immunoassays. As little as 1 mg of amphetamine per liter was easily detected. Results for 266 patients' urines agreed completely with those by gas-liquid chromatography. When a nonseparation enzymoimmunoassay (EMIT-d.a.u., Syva) was applied to 62 specimens chosen without conscious bias, three results were falsely negative, three falsely positive.