APP and early-onset autosomal dominant Alzheimer disease: We measured cerebrospinal fluid (CSF) levels of the soluble isoforms of amyloid precursor protein (APP; sAPPα sAPPβ) and other CSF biomarkers in 107 patients with Alzheimer's disease (AD), dementia with Lewy body dementia (DLB), Parkinson's disease dementia (PDD), and normal controls (NC) using commercial kits.