Prediction of conversion from mild cognitive impairment to Alzheimer's disease by CSF cytochrome c levels and N200 latency.

The aim of the present study was to investigate the role of CSF cytochrome c levels and auditory event-related potentials (AERPs) on the progress of mild cognitive impairment (MCI) to Alzheimer's disease (AD). Fifty one patients diagnosed with MCI and fourteen healthy individuals underwent lumbar puncture at baseline and their CSF cytochrome c levels were determined. A follow-up examination of cytochrome c levels took place in 20 patients after 11 months and in this period five of the patients progressed to AD. ERP examinations were also performed in all patients both at baseline and follow-up. MCI patients had significantly higher cytochrome c levels compared to healthy controls (Mann-Whitney test, Z=-2.110, p=0.018). Compared to MCI patients who remained stable, the AD-converters, had a higher increase over time in cytochrome c levels (Mann-Whitney test, p=0.002; effect size r=0.63) and significantly prolonged N200 latency (Mann-Whitney test, p<0.001; effect size r=0.50). Amongst investigated ERP variables, only N200 amplitude was significantly correlated with CSF cytochrome c levels (rs=0.310, p=0.03). Both parameters were proved capable of discriminating AD converters from those MCI patients who remained stable, with sensitivity and specificity >75%. Our results suggest that conversion from MCI to AD is associated with a marked elevated N200 latency at baseline and a high increase in cytochrome c levels during a relatively short period of time, and that both parameters could be possibly considered as candidate markers for the discrimination between MCI patients who convert to AD and those who remain stable.