CSF Aβ 1-42, but not p-Tau 181, differentiates aMCI from SCI.

AIM: Individuals with amnestic mild cognitive impairment (aMCI) are at a high risk to develop Alzheimer's disease (AD). We compared CSF levels of biomarkers of amyloidosis (Aβ1-42 ) and neurodegeneration (p-Tau181 ) in individuals with aMCI and with subjective cognitive impairment (SCI) in order to ascertain diagnostic accuracy and predict the odds ratio associated with aMCI.

METHODS: We collected CSF of individuals clinically diagnosed with aMCI (33) and SCI (12) of a memory clinic of Southern Brazil. Levels of Aβ1-42 and p-Tau181 were measured by immunoenzymatic assay. Participants also underwent neuropsychological testing including the verbal memory test subscore of the Consortium to Establish a Registry for Alzheimer's Disease (VM-CERAD).

RESULTS: CSF concentration of Aβ1-42 was significantly lower (p: .007) and p-Tau181 /Aβ1-42 ratio higher (p: .014) in aMCI individuals than in SCI. However, isolate p-Tau181 levels were not associated with aMCI (p: .166). There was a statistically significant association between Aβ1-42 and p-Tau181 (R2 : 0.177; β: -4.43; p: .017). ROC AUC of CSF Aβ1-42 was 0.768 and of the p-Tau181 /Aβ1-42 ratio equals 0.742. Individuals with Aβ1-42  < 823 pg/mL levels were 6.0 times more likely to be diagnosed with aMCI (p: .019), with a 68.9% accuracy. Those with p-Tau181 /Aβ1-42 ratio > 0.071 were at 4.6 increased odds to have aMCI (p: .043), with a 64.5% accuracy. VM-CERAD was significantly lower in aMCI than among SCI (p: .041).

CONCLUSION: CSF Aβ1-42 , but not p-Tau181, level was significantly associated with aMCI.