Biomarkers of dementia: comparison of electrochemiluminescence results and reference ranges with conventional ELISA.

We compared the performance of the Meso Scale Diagnostics electrochemiluminescence (MSD) multiplex assay for t-tau and p-tau(231), originally developed for measurement of brain cell extract and tissue cultures, with the established standard method, the Innogenetics ELISA for total and p-tau(181). The methods were also clinically evaluated with 120 samples from our mono center population. The established Innogenetics ELISA procedures have been well optimized to measure patient samples in the normal and pathological range. Compared to the MSD they were superior in the limit of detection for total as well as p-tau. The obtained reference values for our normal controls were in the upper third of the published studies. Innogenetics tau, Innogenetics p-tau(181) and MSD t-tau differentiated the Alzheimer's (n=44) and minimal impairment group (MCI, n=39) from normal controls (n=37), but the MCI group was not statistically different from the normal controls. The MSD multiplex assay measured t-tau adequately but p-tau(231) could not differentiate normal from pathological results in CSF due to the high limit of detection. Both procedures however, have to be further standardized and complemented by adequate internal and external quality control schemes to qualify for routine analysis in a medical laboratory.