Bedside assessment of dementia type using the qualitative evaluation of dementia

Problem: We present a novel dementia assessment instrument, the Qualitative Evaluation of Dementia (QED), designed to discriminate dementia type at the bedside. The QED is a brief, clinically based checklist which opera-tionalizes the approach of a geriatric psychiatrist to the qualitative assessment of dementing illnesses. Scores range from 0 = pure "subcortical" illness, to 30 = pure "cortical" disease. Internal consistency (Chronbach's a =.69) and interrater reliability (r =.93) are acceptable. Blinded raters agree on dementia type in >90% of cases. When QED scores are mapped against measures of general cognitive function a qualitative picture of dementia typology emerges. Method: The QED's ability to discriminate NINCDS "Probable" Alzheimer's disease (AD) from those with "no dementia" and "dementia without cortical features" was assessed in a cross-sectional sample of 118 consecutive patients presenting to a multidisciplin-ary geriatric assessment clinic and consultation service. Results: The QED accurately discriminated all three study groups. When combined with the Executive Interview (EXIT), 87.7% of subjects were correctly classified. Misclassification rates ranged from 11.8% for "Probable" AD to 13% for "no dementia." Substituting the Mini-Mental State Examination (MMSE) correctly classified 74% of subjects, with misclassification rates ranging from 11.8% for "Probable" AD to 40.0% for "dementia with no cortical features." The EXIT was more sensitive than the MMSE to mild cognitive impairment, and subcortical dementia. Conclusions: These results suggest that dementia subtypes can be accurately and reliably assessed using a combination of the QED and either the EXIT or the MMSE. This evaluation can be completed in 20 minutes, and requires no access to blood or laboratory work. The use of the EXIT in this assessment reduces misclassification rates and improves sensitivity in early stages. The implications of this technique for clinical assessment, subject recruitment, and the conceptualization of dementia are discussed.