The Utility of Apolipoprotein E Genotyping in the Diagnosis of Alzheimer Disease in a Community-Based Case Series

Abstract

Context A recent collaborative study found that apolipoprotein E (APOE) genotype, in conjunction with the clinical diagnosis of Alzheimer disease (AD), was useful in improving diagnostic specificity (correctly not diagnosing AD) relative to the clinical diagnosis alone. Since these samples are particularly enriched with patients with AD and the APOE epsilon4 allele, results may not be generalizable to patients seen in the general medical community. Objective To evaluate the diagnostic utility of the APOE genotype in diagnosing AD in a community-based case series from the largest health maintenance organization in an urban area. Design We examined the effect of including APOE genotype on the diagnosis of AD in a community-based case series of patients presenting with memory complaints. Patients Clinical and neuropathologic diagnoses and APOE genotype were obtained from 132 patients who underwent evaluation for dementia and subsequent autopsy. Main outcome measures Sensitivity, specificity, and positive and negative predictive values given various combinations of clinical diagnoses and the presence of an APOE epsilon4 allele. Results Of the 132 patients, 94 had neuropathologically confirmed AD, yielding a prevalence of 71%. The clinical diagnosis alone yielded a sensitivity of 84%, an estimated specificity of 50%, and positive and negative predictive values of 81% and 56%, respectively. The presence of an epsilon4 allele alone was associated with an estimated sensitivity of 59%…