The object of the present invention is to provide: a test kit for an antibody titer or an antibody against a periodontal disease-causing bacterium in a blood sample, which enables the testing on a periodontal disease in patients having a wide scope of immunotypes with high accuracy and can be treated by an automated device at a high speed; a periodontal disease-causing bacterium antigen protein which can be suitably used in the kit; a method for testing an antibody titer or the presence of an antibody in a blood sample using the kit; and a kit for typing strains of Porphyromonas gingivalis. The present invention discloses: a test kit comprising a set of polypeptides respectively having the acid sequences represented by SEQ ID NOs: 1, 3, 9, 15, 19, 31, 41, 43, 63, 65 and 67; a modified polypeptide having the amino acid sequence represented by SEQ ID NO: 67; and a method for determining an antibody titer or the presence of an antibody against a periodontal disease-causing bacterium in a blood sample separated from a human body, comprising bringing the blood sample into contact with the above-mentioned set of polypeptides.