The diagnosis of AD is not made by a measurement scale. The diagnosis of AD is a clinical diagnosis and in ADNI the clinical diagnosis is made according to standard published criteria. To read these criteria please go to the Clinical Core Procedures Manual and thse criteria are described.
The Diagnosis of AD pathology is now also made using amyloid phenotyping which includes amyloid PET imaging and CSF measurements of AB protein. These are also described the various procedure manuals of ADNI