Cystatin C as biological marker in mild cognitive impairment predicting for VAD

Abstract

Nowadays, there are no consistence evidences of the existence of a biological marker for Mild Cognitive Impairment (MCI) able to indicate the course of cognitive deficits. Cystatin C (Cys C) has been already studied as possible biological marker in the cerebrospinal fluid (CSF) in which the protein concentration increases in patients with Vascular Dementia (VAD) when compared to Alzheimer disease subjects (AD) and controls. Nevertheless, this finding was not confirmed at peripheral levels. to investigate the plasma levels of Cys C as putative biological marker for dementias (AD and VAD) and for MCI. Forty-eight patients with MCI (28 of vascular type-vMCI and 20 of amnesic type-aMCI), 26 with VAD, 34 with AD and 24 CTR were included. Cys C concentration {Cys C} in plasma samples was evaluated using ELISA test. compared with CTR, mean {Cys C} was increased in patients with MCI (p<0.05). A cut-off score of 2.3 mg/L separate MCI from CTR with 70% of sensitivity and 68% of specificity. Moreover, {Cys C} in VAD were significantly higher than AD (p<0.0001); a cutoff score of 1.7 mg/L separated VAD from AD with 95% of specificity and 85% of sensitivity. {Cys C} in vMCI is increased as compared to aMCI (p<0.001). A cutoff of 3.1 mg/L separated vMCI from aMCI patients with 70% of specificity and 60% of sensitivity. Cys C could be used as specific marker able to identify cognitive decline, distinguish the cognitive decline between amnesic and vascular type and also make a distinction between VAD and AD diagnosis. Longitudinal studies are now needed to investigate if Cys C could be also a prognostic marker predicting the conversion to VAD.