Comparison of clinical state, retrospective informant interview and the neuropathologic diagnosis of alzheimer's disease

This study compared clinical diagnosis of dementia derived from medical records and a retrospective version of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) against the criterion of neuropathology. Subjects comprised 50 consecutive patients who died in a geriatric hospital in Melbourne and underwent necropsy. All informants were seen within 3.5 years of death. Discordance between clinical and pathological diagnosis occurred in seven (14%) cases. The IQCODE scores for the group with a clinical diagnosis of Alzheimer's disease (mean ± SD) were 4.28 ± 0.78 and were significantly different from the non‐demented group, 3.39 ± 0.51, p < 0.001. Similarly, IQCODE scores were significantly different between the groups with and without a pathologic diagnosis of Alzheimer's disease, 4.21 ± 0.70 and 3.51 ± 0.79 respectively, p < 0.01. Using immunohistochemical techniques instead of conventional methods to make a diagnosis of Alzheimer's disease, there were significant differences in IQCODE scores between the Alzheimer's group, 4.13 ± 0.83, and the group with normal neuropathology, 3.45 ± 0.54, p < 0.01. These data support the conclusion that when used retrospectively, the IQCODE is a valid screening test for dementia using neuropathological diagnosis as the criterion.