A STANDARDIZED TECHNIQUE FOR ESTABLISHING ONSET AND DURATION OF SYMPTOMS OF ALZHEIMERS-DISEASE

Objectives: To develop an informant-based semistructured interview to determine the onset and duration of symptoms of Alzheimer's disease, a nd to use this instrument with informants to characterize a cohort of mildly impaired patients with Alzheimer's disease. Design: In study 1, interrater and interinformant reliability was examined for the date o f onset and the order of appearance for specific symptoms that were el icited by the semistructured onset interview. In study 2, the instrume nt was used to characterize disease onset in a cohort of patients with Alzheimer's disease who were participating in a large multicenter stu dy. Subjects: Informants of patients with Alzheimer's disease. Results : In study 1, interrater reliability for duration of illness was excel lent (intraclass correlation coefficient = .99, P < .001), and interin formant reliability was good (intraclass correlation coefficient = .86 , P < .001). Agreement for the presence of a given symptom was highest for those that were most commonly reported leg, memory and performanc e difficulty). In study 2, 89% of the cohort had memory problems, and 63.9% had performance difficulties as the first or second symptom. Dep ression and language problems were less commonly reported. Psychosis a nd behavioral disturbances were rarely reported as the first problem. Conclusion: This instrument provides a reliable procedure for standard izing the estimation of duration of illness based on retrospective rep ort.