Abstract: A problem to be solved by the invention is to improve the sensitivity of measurement of an analyte in a sample by a sandwich immunoassay. The sensitivity can be improved significantly in a sandwich immunoassay using a first antibody and a second antibody when one or both of the first antibody and the second antibody are a mixture of a monoclonal antibody recognizing a linear epitope and a monoclonal antibody recognizing a conformational epitope.

Abstract: A problem to be solved is to provide a glycated hemoglobin (%) assay method and assay reagent capable of accurate measurement of glycated hemoglobin (%) in blood even when a blood specimen containing hemoglobin contains abnormal hemoglobin such as HbS or HbC. The present invention provides a method capable of accurate measurement of glycated hemoglobin (%) in blood even in a specimen containing abnormal hemoglobin by combining two types of monoclonal antibodies, i.e., an anti-glycated hemoglobin monoclonal antibody and a monoclonal antibody to the anti-glycated hemoglobin monoclonal antibody, and an assay reagent for performing the method.