Immunochromatographic assay method, and test strip used in said immunochromatographic assay method

An immunochromatographic test strip comprising following (1) to (3):

• (1) a sample pad containing a sample application region for applying a biological sample that may contain an analyte;
• (2) an insoluble membrane containing at least one detection region to which a binding partner immunologically reactive with the analyte is immobilized, wherein the insoluble membrane contains a cationic substance;
• and
• (3) a conjugate containing a binding partner immunologically reactive with the analyte, wherein the binding partner is immobilized to a label.

A method of suppressing non-specific reaction in an immunochromatographic assay method for an analyte, the method comprising using a test strip comprising following (1) to (3):

• (1) a sample pad containing a sample application region for applying a biological sample that may contain the analyte;
• (2) an insoluble membrane containing at least one detection region to which a binding partner immunologically reactive with the analyte is immobilized, wherein the insoluble membrane contains a cationic substance;
• and
• (3) a conjugate containing a binding partner immunologically reactive with the analyte, wherein the binding partner is immobilized to a label.