The Diagnosis of Dementia: Diagnostic Accuracy of an Instrument Measuring Activities of Daily Living in a Clinic-Based Population

Abstract

Background/Aims: Since widely accepted definitions of dementia encompass impairments in social and occupational, as well as cognitive, function, we investigated the diagnostic accuracy of Lawton and Brody’s Instrumental Activities of Daily Living (IADL) Scale as an independent test for the diagnosis of dementia. Methods: The IADL Scale was administered to consecutive referrals to 2 memory clinics over a 2-year period, independent of other tests (interview, neuropsychology, imaging) which were used to establish diagnoses according to standard diagnostic criteria, and the results were compared. Results: In a cohort of 296 patients, 52% adjudged to have dementia, IADL Scale scores and subscores showed low sensitivity, specificity, and positive and negative predictive values for the diagnosis of dementia. The likelihood ratios, a measure of diagnostic gain, were generally small to unimportant, and diagnostic accuracy as measured by area under the receiver operating characteristic curve was no better than 0.75. Conclusion: IADL Scale scores are not very helpful in making a diagnosis of dementia. More sensitive scales may be required to detect dementia-related functional decline, although it is also possible that dementia syndromes may be present in the absence of functional decline, challenging accepted definitions of dementia.