The combination of cognitive testing and an informant questionnaire in screening for dementia.

AIM A cognitive test and an informant report questionnaire were used together to investigate whether their combined use could improve the accuracy of detecting dementia in a memory clinic, compared with either test used alone. METHOD The subjects were 323 patients assessed at a memory clinic. The Mini-Mental State Examination and the short form of the Informant Questionnaire on Cognitive Decline in the Elderly were used. A method of combining the test scores developed by Mackinnon and Mulligan [Am J Psychiatry 1998; 155: 1529-35] was used. Dementia was diagnosed according to Diagnostic and Statistical Manual of Mental Disorders, Third Edition-Revised criteria. RESULTS Logistic regression analysis showed that the combination of the Mini-Mental State Examination and the Informant Questionnaire on Cognitive Decline in the Elderly produced a slightly more accurate prediction of dementia caseness than either test used alone. Using receiver operating characteristic analysis the performance of the combination of the tests according to a weighted sum rule was compared with the performance of either test used alone. This way of combining the tests resulted in a more accurate screening for dementia than when the Informant Questionnaire on Cognitive Decline in the Elderly was used alone. The area under the receiver operating characteristic curve for the Mini-Mental State Examination combined with the Informant Questionnaire on Cognitive Decline in the Elderly was 0.89 compared with 0.82 for the Informant Questionnaire on Cognitive Decline in the Elderly alone (chi-square = 10.63; P = 0.0011). However, there was no improvement in screening performance when the combination of Mini-Mental State Examination and Informant Questionnaire on Cognitive Decline in the Elderly was compared with the Mini-Mental State Examination used alone (area under the receiver operating characteristic curve = 0.89 versus 0.86; chi-square = 3.54; P = 0.060). CONCLUSION The combination of cognitive testing and an informant report according to a weighted sum rule in this population did not result in any advantage over the use of the Mini-Mental State Examination alone. The mixed results of this study contrast with those of Mackinnon and Mulligan.