The observed GM-CBF differences between Aβ-positive CI and the CU groups are consistent with the accumulating evidence demonstrating widespread hypoperfusion across different cortical regions in AD.51, –53 Additional correction for the APOE ε4 genotype did not attenuate the observed effect sizes suggesting that between group GM-CBF differences are independent of APOE ε4 status. The gene discussed is APOE; the disease is Alzheimer disease.