DUAL ANALYTE ASSAY BASED ON PARTICLE TYPES OF DIFFERENT SIZE MEASUREDBY FLOW-CYTOMETRY

Simultaneous flow cytometric assays have been developed for alpha-feto protein (AFP) and human chorionic gonadotropin (hCG), with internal de termination of sample related non-specific binding (NSB). The assays u se particles of 7.5, 6.5 and 5.5 mu m diameter coated with, respective ly, monoclonal antibodies specific for AFP, hCG or an epitope normally not present in serum. The different particle types were identified si multaneously by light-scatter measurements as their specific immunoflu orometric responses were determined. The NSB in the simultaneous assay of AFP and hCG was increased by similar to 30% compared to correspond ing single analyte assays. The working range of the dual analyte assay s was 0.6-2000 kIU/l for AFP and 6-10000 IU/l for hCG. No significant interference from the presence of the other analyte was observed in th e measurement of either AFP or hCG. The 95% confidence interval for th e ratio of dual over single analyte assay results was [0.81, 1.11] for AFP and [0.88, 1.16] for hCG.