DCD and Alzheimer disease: Another serum‐based biomarker signature with pro‐protein convertase subtilisin/kexin type 9 (PCSK9), coagulation factor XIII, A1 polypeptide (F13A1), and dermcidin (DCD) was identified using liquid chromatography–tandem MS (LC–MS/MS) for the prediction of AD, followed by validation by enzyme‐linked immunosorbent assay and western blotting.94