Abstract: Provided is a method of detecting a target substance by which the target substance can be detected with efficiency and a high sensitivity, and in a simple manner, a target substance detection polymer used in the method, and a method of forming the polymer. The method of detecting a target substance includes the steps of: (A) forming a target substance detection polymer by causing multiple kinds of nucleic acid probes for forming a polymer to react with a binding probe having a region capable of binding to the target substance and a region capable of binding to at least one of the nucleic acid probes in a solution; (B) binding the target substance detection polymer and the target substance; and (C) detecting the target substance detection polymer to which the target substance is bound.

Abstract: Provided are a signal amplification method of improving signal sensitivity, qualifying properties and handling property in detection of a target gene by using a PALSAR method, a method of detecting a target gene by using the method, and an oligonucleotide probe to be used in the method. A signal amplification method in detection of a target gene using a polymer formed by the use of a plurality of kinds of oligonucleotide probes having complementary base sequence regions capable of hybridizing with each other, including labeling at least one of the plurality of kinds of oligonucleotide probes with acridinium ester for detection.

Abstract: The present invention provides an immunoassay for specifically measuring with high sensitivity PIVKA-II in serum or plasma through antigen-antibody reaction by adding an animal serum containing thrombin and/or an antibody reacting with human fibrin-like related substances to the reagents. The immunoassay of the invention comprises the steps of adding thrombin and/or an antibody reacting with human fibrin-like related substances to the reagents, and measuring PIVKA-II in serum or plasma.