For example, the studies by Drzezga et al. (32 patients with moderate AD) [81], Rowe et al. (53 patients with mild AD) [95], and Lehmann et al. (52 patients with probable AD) [98] each utilized Pittsburgh Compound B (PIB) PET analysis on age- and cognition-matched AD patients who were confirmed to be Aß-positive, but with each study arriving at a different conclusion about the relative levels of Aß in APOE4+ vs. APOE4− AD patients. The gene discussed is APOE; the disease is Alzheimer disease.