Serum concentration of alpha 1-antichymotrypsin is elevated in patients with senile dementia of the Alzheimer type.

Levels of the serum protease inhibitors (alpha 1-antichymotrypsin, alpha 1-antitrypsin, and inter-alpha-trypsin inhibitor) were measured in patients with senile dementia of the Alzheimer type (SDAT) to determine whether these levels might be useful as diagnostic markers of SDAT. The levels of alpha 1-antichymotrypsin were found to have no relationship to either age or sex. The SDAT group showed levels of alpha 1-antichymotrypsin significantly higher than those of any of the following groups: normal control group (p less than 0.001), vascular dementia group (p less than 0.01), mixed type dementia group (p less than 0.05), and 3 other groups (Parkinson's disease, spinocerebellar degeneration, cerebrovascular disease) (p less than 0.001). The serum concentration of alpha 1-antichymotrypsin seemed to increase slightly in advanced stages of the disease. The serum levels of both alpha 1-antitrypsin and inter-alpha-trypsin inhibitor differed insignificantly in comparison of the SDAT group and normal control group. Of the 3 serum protease inhibitors measured, only alpha 1-antichymotrypsin was found to increase significantly in SDAT. These findings suggest that the measurement of serum concentration of alpha 1-antichymotrypsin may prove useful as a diagnostic marker of SDAT.