Item Response Theory Reveals Variability of Functional Impairment within Clinical Dementia Rating Scale Stages

BACKGROUND/AIMS: To investigate whether an item response theory (IRT) approach to measuring variations of dementia severity within Clinical Dementia Rating (CDR) stages is associated with activities of daily living (ADLs). METHODS: IRT estimates of dementia severity within CDR stages in 1,181 patients were correlated with ADLs and analyzed. RESULTS: IRT-determined dementia severity was significantly correlated with ADLs in three of four impaired dementia stages. CONCLUSION: An IRT approach shows considerable advantages over traditional scoring practices of the CDR not only because it increases precision in dementia measurement, but also because it enables one to discover more precise associations with functional outcomes such as ADLs.