As biomarkers in plasma several substances have been examined, e.g. isopostane, 3-nitrotyrosin, α-1-antichymotrypsin, interleukines, C-reactive protein, C1q complementary systems, 24S-hydrocholesterol, homocysteine, but none of these markers had enough sensitivity or specificity to diagnose AD [100, 134]. Here, CRP is linked to Alzheimer disease.