ANALYTE AND LABEL BINDING ASSAY READ BY FLOW-CYTOMETRY

A new immunometric two-site sandwich assay is introduced, in which a l abel-scavenging binding partner is added to the sample in addition to the analyte-binding partner, The scavenger binding partner binds exces s label antibody, giving a signal proportional to the amount of excess label antibody in the sample solution. A set of two calibration curve s is obtained from the two binding partners simultaneously, and a comb ination of the two signals gives an unambiguous determination of the a nalyte concentration, even for high analyte concentrations where the h ook effect may occur. Two-particle immunofluorometric assays developed for placental alkaline phosphatase and human chorionic gonadotropin o n the basis of this principle and yielding signals measured by flow cy tometry gave rapid results (2 h) and had working ranges in excess of 5 and 6 orders of magnitude for the respective analytes.