Immunochromatographic test strip and detection method using immunochromatography for detecting target in red blood cell-containing sample

An immunochromatographic detection method, comprising the steps of:

• (A) supplying a sample to a sample-supply portion of a test strip comprising a membrane consisting of a porous body equipped with at least a sample-supply portion, a spreading portion, and a detecting portion,
• wherein a conjugate comprising a colloidal gold sensitized with an antibody to an object is retained in a dissoluble manner in a part of the spreading portion, and an antibody is immobilized in the detecting portion which is a part of the spreading portion on the downstream side relative to the conjugate-retaining part;
• (B) agglutinating a blood-derived component in the sample through contact between polybrene and the sample in the sample-supply portion or in the upstream of the sample-supply portion;
• (C) separating and removing aggregates acquired at step (B) from the sample;
• (D) bringing a sample component acquired at step (C) after separation and removal of the aggregates into contact with the colloidal gold-containing conjugate, the step being performed in the presence of a buffer solution having ability to suppress aggregation of the conjugate due to polybrene;
• and
• (E) detecting a complex of the object in the sample component and the conjugate acquired at the step (D) in the detecting portion, and
• wherein the buffer solution component is selected from a group consisting of Bis-Tris, MES, and citric acid.