Patent ID: 7867725

Claim:
A method of identifying fragments of osteopontin peptide as being C-terminal fragments of osteopontin peptide or N-terminal fragments of osteopontin peptide, the method comprising: a) capturing the osteopontin fragments with a capture antibody which binds specifically to a first C-terminal epitope of osteopontin peptide in a first assay position and a first N-terminal epitope of osteopontin peptide in a second assay position; b) detecting the presence of captured osteopontin fragments, if any, of the first and second assay positions with a second antibody specific for a second C-terminal epitope of osteopontin peptide in the first assay position and a second antibody specific for a second N-terminal epitope of osteopontin in the second assay position; and c) determining i) if any peptides captured in the first assay position as detected by the detecting antibody are C-terminal fragments with a determination antibody which specifically binds a first or second N-terminal epitope of osteopontin, the lack of binding of the determination antibody in the first assay position in view of the binding of the detection antibody being indicative of the presence of C-terminal osteopontin fragments in the first assay position and; determining ii) if any captured osteopontin peptides in the second assay position as detected by the detection antibody are N-terminal fragments with a determination antibody which specifically binds a first or second C-terminal epitope of osteopontin, the lack of binding of the determination antibody in the second assay position in view of the binding of the detection antibody being indicative of the presence of N-terminal osteopontin fragments in the second assay position, as compared to a control sample comprising a full length osteopontin peptide.