Assay

The present invention offers the assay kit for detecting the object sample in a sample. This kit contains a fixed capture reagent combinable with the sign kind which has the 1st coupling field combinable with a reporter kind and the sample for b, and the 2nd coupling field combinable with a reporter kind, a fixed kind combinable with the 1st coupling field of c sign kind, and d reporter kind. Although contact a sample as a sign species, a fixed kind is subsequently made to contact and a fixed capture reagent is made to contact after that, before contacting a sample into a fixed capture reagent, the procedure which adds a reporter kind is taken. When a sample does not exist in a sample, it combines with a fixed kind, therefore a sign kind cannot be combined with a fixed capture reagent. When a sample exists in a sample, and a sample combines with a sign kind, a sign kind cannot be combined with a fixed kind, but it is judged by existence of the sign kind which can be combined with a fixed capture reagent through a reporter kind, therefore existence of a sample combines with a fixed capture reagent through a reporter kind.