Abstract: Disclosed are a PIVKA-II measurement method that achieves better serum-plasma correlation than conventional methods, and a reagent and a kit therefor. The PIVKA-II measurement method according to the present invention comprises measuring PIVKA-II in a sample by an immunoassay using a mixture of an anti-F1 antibody that specifically binds to prothrombin fragment F1 or an antigen-binding fragment thereof and an anti-F2 antibody that specifically binds to prothrombin fragment F2 or an antigen-binding fragment thereof; and an anti-PIVKA-II antibody that specifically binds to PIVKA-II or an antigen-binding fragment thereof.

Abstract: The present invention aims to provide an assay reagent and an assay for accurately measuring KL-6, in particular, an assay reagent and an assay for accurately measuring KL-6 in samples containing a rheumatoid factor and/or a nonspecific substance other than the rheumatoid factor. KL-6 in samples that contain a rheumatoid factor and/or a nonspecific substance other than the rheumatoid factor can be accurately measured using an immunoassay reagent comprising a solution at a pH of 4.0 to 5.5 containing a rheumatoid factor interference inhibitor and a solution of an insoluble carrier on which anti-KL-6 antibodies are immobilized.

Abstract: A problem to be solved by the present invention is to inhibit a nonspecific agglutination reaction in an agglutination test using a monoclonal antibody having a property of specifically biding to PIVKA-II and a monoclonal antibody having a property of specifically biding to prothrombin as well as two types of carrier particles carrying these monoclonal antibodies. The nonspecific agglutination reaction can be inhibited by adding certain divalent metal ions to a reaction solution containing the monoclonal antibody having a property of specifically biding to PIVKA-II and the monoclonal antibody having a property of specifically biding to prothrombin as well as the two types of carrier particles carrying these monoclonal antibodies.

Abstract: The present invention aims to provide an assay reagent and an assay for accurately measuring KL-6, in particular, an assay reagent and an assay for accurately measuring KL-6 in samples containing a rheumatoid factor and/or a nonspecific substance other than the rheumatoid factor. KL-6 in samples that contain a rheumatoid factor and/or a nonspecific substance other than the rheumatoid factor can be accurately measured using an immunoassay reagent comprising a solution at a pH of 4.0 to 5.5 containing a rheumatoid factor interference inhibitor and a solution of an insoluble carrier on which anti-KL-6 antibodies are immobilized.

Abstract: The present invention provides a method for diagnosis of cystic fibrosis, the method comprising: measuring an amount of KL-6 in a sample of body fluid from a subject, and determining, based on the amount of KL-6 measured, the degree of presence of cystic fibrosis in the subject.