1. A method for qualifying Alzheimer's disease status in a subject comprising: (a). measuring at least one biomarker in a CSF sample from the subject, wherein said at least one biomarker consists of residues 35-121 of SEQ ID NO:4; (b). comparing the level of the biomarker in said subject to a diagnostic cut-off level; and (c). correlating the measurement with Alzheimer's disease status, wherein elevated levels of the biomarker in said CSF sample relative to said diagnostic cut-off level are indicative of an increased likelihood of Alzheimer's disease in said subject.