This model identified four proteins (secreted modular calcium-binding protein 1 (SMOC1), noggin (NOG), amyloid P component, serum (APCS), and netrin-1 (NTN1)) based upon the significance of feature frequency, among which SMOC1 displayed a positive feature coefficient—i.e., an increased level of this protein was associated with an increased probability of classification as AD (Supplementary Fig. 1a). Here, SMOC1 is linked to Alzheimer disease.