BACKGROUND: Clinicopathological studies suggest that Alzheimer's disease (AD) 
pathology begins ∼10-15 years before the resulting cognitive impairment draws 
medical attention. Biomarkers that can detect AD pathology in its early stages 
and predict dementia onset would, therefore, be invaluable for patient care and 
efficient clinical trial design. We utilized a targeted proteomics approach to 
discover novel cerebrospinal fluid (CSF) biomarkers that can augment the 
diagnostic and prognostic accuracy of current leading CSF biomarkers (Aβ42, tau, 
p-tau181).
METHODS AND FINDINGS: Using a multiplexed Luminex platform, 190 analytes were 
measured in 333 CSF samples from cognitively normal (Clinical Dementia Rating 
[CDR] 0), very mildly demented (CDR 0.5), and mildly demented (CDR 1) 
individuals. Mean levels of 37 analytes (12 after Bonferroni correction) were 
found to differ between CDR 0 and CDR>0 groups. Receiver-operating 
characteristic curve analyses revealed that small combinations of a subset of 
these markers (cystatin C, VEGF, TRAIL-R3, PAI-1, PP, NT-proBNP, MMP-10, MIF, 
GRO-α, fibrinogen, FAS, eotaxin-3) enhanced the ability of the best-performing 
established CSF biomarker, the tau/Aβ42 ratio, to discriminate CDR>0 from CDR 0 
individuals. Multiple machine learning algorithms likewise showed that the novel 
biomarker panels improved the diagnostic performance of the current leading 
biomarkers. Importantly, most of the markers that best discriminated CDR 0 from 
CDR>0 individuals in the more targeted ROC analyses were also identified as top 
predictors in the machine learning models, reconfirming their potential as 
biomarkers for early-stage AD. Cox proportional hazards models demonstrated that 
an optimal panel of markers for predicting risk of developing cognitive 
impairment (CDR 0 to CDR>0 conversion) consisted of calbindin, Aβ42, and age.
CONCLUSIONS/SIGNIFICANCE: Using a targeted proteomic screen, we identified novel 
candidate biomarkers that complement the best current CSF biomarkers for 
distinguishing very mildly/mildly demented from cognitively normal individuals. 
Additionally, we identified a novel biomarker (calbindin) with significant 
prognostic potential.