Objective

To determine the validity of the Dementia Questionnaire (a semistructured informant interview) for the diagnosis of dementia.

Design

Comparison of dementia status determined by a telephone-administered informant questionnaire with the criterion standard of clinical diagnosis established by examination and laboratory studies.

Setting

Gerontology Research Center, the Baltimore Longitudinal Study of Aging.

Subjects

Volunteer cohort of 42 men and 32 women aged 68 to 97 years. Subjects were selected from strata defined by Blessed Information Memory Concentration Test scores, with oversampling of borderline scores (3 to 10).

Main outcome measures

Sensitivity and specificity of the Dementia Questionnaire in comparison with the criterion standard of clinical diagnosis.

Secondary outcome measure

Interrater reliability (kappa coefficient).

Results

Sensitivity and specificity for dementia were 100% and 90%, respectively. Most false-positive findings were from subjects with cognitive impairment that did not meet criteria for dementia (Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition. Interrater reliability was high (kappa = 0.83).

Conclusion

The Dementia Questionnaire can be used effectively in research studies to screen for dementia.

Objective

To determine the sensitivity and specificity of postmortem dementia diagnoses based on a retrospective informant interview by comparison with criterion standard neuropathological diagnoses and the results of previous clinical examinations.

Setting

Three university-based academic research centers.

Subjects

Fifty-four deceased elderly persons with Alzheimer disease, another dementing disorder, a neurologic disease resulting in functional impairment but no dementia, or no neurologic disorder.

Methods

Blinded nonclinician interviewers administered the Dementia Questionnaire (DQ) by telephone to informants, typically close relatives, who were familiar with the intellectual and functional status of the subjects before death. Two senior clinicians (LJ.T. and C.K.) rated each DQ for the presence or absence of a dementia syndrome during life and for the specific disorders causing the dementia, if present. Raters were blinded to the neuropathological findings and based their assessments only on data provided by responses to the DQ. Comparison was made with diagnoses based on neuropathological assessment. In most cases, the results of antemortem clinical examinations were also available as a check on the clinical diagnosis of the dementia syndrome. Sensitivity and specificity of the DQ diagnoses were computed, and chance-corrected agreement measures were calculated for the 2 independent DQ raters (LJ.T. and C.K.).

Results

Compared with antemortem clinical diagnosis, the average sensitivity of the DQ for the clinical syndrome of dementia was 92.8%, the specificity was 89.5%, and the interrater agreement was 98% (kappa = 0.96). Among 7 subjects with mild dementia (Mini-Mental State Examination score > or = 24 at the last clinical examination), 5 (71%) were correctly identified using the DQ. The DQ correctly indicated the absence of dementia in 8 (80%) of 10 subjects with other neurologic disorders causing functional impairment. Compared with the neuropathological diagnoses, the DQ differentiated Alzheimer disease from other primary causes of dementia with a sensitivity of 89% and a specificity of 72%. The interrater agreement was 93.8% (kappa = 0.85).

Conclusions

Compared with the results of the antemortem clinical examinations, the DQ was sensitive to the presence of dementia, detected most cases of mild dementia, and discriminated dementia from other neurologic disorders causing functional impairment. Compared with the neuropathological diagnoses, the ability of the DQ to differentiate Alzheimer disease from other dementing disorders indicates that it may be useful as a research tool.