Decreased salivary lactoferrin levels are specific to Alzheimer’s disease

Abstract Background Efforts focused on developing new less invasive biomarkers for early Alzheimer’s disease (AD) diagnosis are substantial. Evidences of infectious pathogens in AD brains may suggest a deteriorated innate immune system in AD pathophysiology. We previously demonstrated reduced salivary levels of Lf in AD patients, one of the major antimicrobial peptides. Methods To assess the clinical utility of salivary Lf for AD diagnosis, we examine the relationship between salivary Lf and cerebral amyloid-β (Aβ) load in two different cross-sectional cohorts including patients with different neurodegenerative disorders. Study participants for cohort 1 (n = 116) were enrolled from the 12 de Octubre University Hospital Neurology Service in Madrid (Spain) and Pablo de Olavide University in Sevilla (Spain). Study participants for cohort 2 (n = 142) were enrolled as part of the Atherobrain - Heart to Head (H2H) project. Participants underwent neurological and neuropsychological examination, saliva sampling, and amyloid-Positron-Emission Tomography (PET) neuroimaging. Results The diagnostic performance of salivary Lf in the cohort 1 had an area under the curve [AUC] of 0.95 (0.911-0.992) for the differentiation of the prodromal AD/AD group positive for amyloid-PET (PET + ) versus healthy group, and 0.97 (0.924-1) versus the frontotemporal dementia (FTD) group. In the cohort 2, salivary Lf had also an excellent diagnostic performance in the health control group versus prodromal AD comparison: AUC 0.93 (95% CI 0.876-0.989). Salivary Lf detected prodromal AD and AD dementia distinguishing them from other dementias as FTD with over 87% sensitivity and 91% specificity. Conclusion Therefore, salivary Lf seems to have a very good diagnostic performance to detect AD. Our findings support the possible utility of salivary Lf as a new non-invasive and cost-effective AD biomarker.