SERPINA1 and Alzheimer disease: No significant correlation was found in the various subgroups (PD: r = −0.102, p = 0.663; PDD: r = 0.428, p = 0.0584; AD: r = 0.169, p = 0.662; FTLD: r = 0.0, p = 1.0), so that we suppose that the Serpin A1 isoform-distribution is a tau-level independent marker for PDD.