CR1 and Alzheimer disease: Some psychometric approaches (e.g., threshold and cluster stratification) using neuropsychological test performance have shown great promise in identifying genetic variants associated with AD.4,5,7–10 For example, employing a cognitively defined threshold stratification using Z-scores on single and multiple domains Mukherjee and colleagues constructed AD subgroups that were associated with different genetic variants.5 Specifically, in the memory only impaired subgroup, several well-known AD risk genes, SORL1, Cass4, and CR1, were associated with memory impairment.