Objectives: the relative difficulties of items on the Mini-Mental State Examination (MMSE) were compared in English-speaking Alzheimer's disease (AD) patients in the United States (US) and United Kingdom (UK).
Methods: participants were aged 75 and over, with a clinical diagnosis of AD according to standardized methods. Initial MMSE scores from an AD patient registry in the US (n = 401), and a field survey in the UK (n = 139) were compared. Item Characteristic Curve analysis (ICC) was used to calculate the relative difficulty of individual MMSE items, adjusted for the remaining MMSE items. Age, gender, education, and severity of disease were evaluated as possible confounders.
Results: UK participants found it relatively more difficult to name their county than US participants did to name their state. The relative difficulties of registration and recall, repeating a phrase, and following verbal directions also were significantly higher for the UK participants, even after adjustment for other factors.
Conclusions: differences between the cohorts could be explained by translation artifacts in the test items or by cultural differences in the manifestation of AD. In this study, most, if not all differences can be explained by the former. ICC analysis can be used to develop tests that are functionally equivalent, a prerequisite for comparing dementia in different populations.
Copyright 2002 John Wiley & Sons, Ltd.