Next, at the serum CD33 protein level, 2 IVs were eligible for the MR analysis, and the IVW results showed that﻿ each one standard deviation increase in serum CD33 protein level was also leading to an increased risk of AD (OR [95% CI] = 1.08 [1.031, 1.139], p = 1.6e-03). This evidence concerns the gene CD33 and Alzheimer disease.