Distinguishing Alzheimer's disease from other dementias. Questionnaire responses of close relatives and autopsy results

Post-Mortem diagnosis of dementia by informant interview

The diagnosis of normal cognition or dementia in the Brazilian Brain Bank of the Aging Brain Study Group (BBBABSG) has relied on postmortem interview with an informant.

OBJECTIVES

To ascertain the sensitivity and specificity of postmortem diagnosis based on informant interview compared against the diagnosis established at a memory clinic.

METHODS

A prospective study was conducted at the BBBABSG and at the Reference Center for Cognitive Disorders (RCCD), a specialized memory clinic of the Hospital das Clínicas, University of São Paulo Medical School. Control subjects and cognitively impaired subjects were referred from the Hospital das Clínicas to the RCCD where subjects and their informants were assessed. The same informant was then interviewed at the BBBABSG. Specialists' panel consensus, in each group, determined the final diagnosis of the case, blind to other center's diagnosis. Data was compared for frequency of diagnostic equivalence. For this study, the diagnosis established at the RCCD was accepted as the gold standard. Sensitivity and specificity were computed.

RESULTS

Ninety individuals were included, 45 with dementia and 45 without dementia (26 cognitively normal and 19 cognitively impaired but non-demented). The informant interview at the BBBABSG had a sensitivity of 86.6% and specificity of 84.4% for the diagnosis of dementia, and a sensitivity of 65.3% and specificity of 93.7% for the diagnosis of normal cognition.

CONCLUSIONS

The informant interview used at the BBBABSG has a high specificity and sensitivity for the diagnosis of dementia as well as a high specificity for the diagnosis of normal cognition.

Accuracy of collateral source reports in very mild to mild dementia of the Alzheimer type

OBJECTIVES

To examine the reporting accuracy of collateral sources (knowledgeable informants) regarding very mild and mild dementia of the Alzheimer type (DAT) and to identify characteristics associated with collateral source accuracy.

DESIGN

Secondary data analysis of initial visits of individuals enrolled in a longitudinal study of healthy aging and Alzheimer disease.

SETTING

Urban Alzheimer disease research center.

PARTICIPANTS

Pairs of 515 individuals with very mild (n = 203) or mild (n = 312) DAT and their collateral sources.

MEASUREMENTS

Collateral sources were asked separately during a semistructured interview by experienced clinicians to report current ability of the individual with DAT in memory, orientation, and judgment and problem solving. The clinical performance of the individuals with DAT in these domains was compared with these predictions.

RESULTS

Collateral sources were consistently and significantly accurate in reporting the cognitive capabilities of individuals with very mild and mild DAT. Although all types of collateral sources performed significantly better than chance, individual variables that correlated with collateral source accuracy included spousal relationship; living with the individual with DAT; frequent exposure to the individual; and age, education level, sex and dementia severity of the individual with DAT.

CONCLUSION

Collateral sources are accurate in reporting the cognitive capabilities of individuals with DAT, even in the very mild stage of dementia.

Validity of family history for the diagnosis of dementia among siblings of patients with late-onset Alzheimer's disease

We examined 180 siblings of 127 probands with probable or possible Alzheimer's dementia (AD) in a family study of AD. The overall sensitivity of a simple family history questionnaire was 64% and the specificity was 84%. Sensitivity improved 90-100% with minimal decline in specificity when we considered clinic-based vs. population survey patients. Higher education among informants and the availability of a spouse or a sibling as informant significantly increased sensitivity. Awareness of such factors may improve the yield of the family history in AD using a simple questionnaire.

A family with multiple instances of definite, probable and possible early-onset Alzheimer's disease

A family with a multigenerational history of proven or suspected early-onset Alzheimer's disease (AD) consistent with autosomal-dominant inheritance is described. To date, the pedigree comprises five generations in which there are 13 known affected individuals. The mean age of onset of cognitive deficits in those for whom data are available (n = 11) is 47.6 (s.d. 3.0) years and the mean age of death (n = 10) is 58.8 (s.d. 4.0) years. The variability in the extent and quality of available data illustrates the diagnostic difficulties encountered in ascertaining such an extended pedigree, and the need for caution in interpreting the evidence.