Method of agglutination immunoassay

A particle enhanced agglutination immunoassay comprising the steps of:

• mixing a sample solution containing an analyte with a solution containing insoluble carrier particles carrying a binding partner or binding partners for the analyte to prepare a mixed solution;
• determining a variation (i) in intensity of light scattered from the mixed solution based on a difference in intensity of scattered light between a first and a second time point;
• determining a variation (ii) in absorbance of the mixed solution based on a difference in absorbance between a third and a fourth time point;
• and
• correlating the determined variation (i) in intensity of scattered light and the determined variation (ii) in absorbance with an amount of the analyte present in the sample using a calibration curve plotted based on the variation in intensity of scattered light and a calibration curve plotted based on the variation in absorbance,
• wherein at a low concentration of analyte, the concentration is determined based on the calibration curve plotted based on the measurement of the intensity of scattered light and at a high concentration of analyte, the concentration is determined based on the calibration curve plotted based on the measurement of the absorbance;
• and
• wherein the time period which is defined by the third and fourth time points and for which the variation (ii) is determined is shorter than the time period which is defined by the first and second time points and for which the variation (i) is determined, and the determining a variation (i) in intensity light scattered and the determining a variation (ii) in absorbance are combined in a single assay.