The Behavioural Dysfunction Questionnaire discriminates behavioural variant frontotemporal dementia from Alzheimer's disease dementia and major depressive disorder

Abstract

Background and objectives: Early-stage behavioural variant frontotemporal dementia (bvFTD) is often misdiagnosed, highlighting the need for new diagnostic instruments. Based on the revised diagnostic criteria for bvFTD, we developed the Behavioural Dysfunction Questionnaire (BDQ). In this explorative study, we aimed to determine the best scoring and analytical method for the BDQ to discriminate between bvFTD and non-bvFTD patients.

Materials and methods: 34 patients with early-stage bvFTD, 56 with early-stage Alzheimer's disease dementia (ADD) and 41 with major depressive disorder (MDD) were recruited. We calculated BDQ-items with or without inclusion of a time criterion: (a) without time criterion, (b) with 10 years' time criterion (symptom presence less than 10 years), and (c) with 3 years' time criterion (symptom presentation within the first 3 years). Using these three differently calculated items, we generated six variables, i.e. 3*2 [BDQ-Global Score (BDQ-GS; domains average score); BDQ-Global Domain Score (BDQ-GDS; domains categorical score)]. Then, we performed univariate and bivariate (BDQ-GS and BDQ-GDS combined) ROC analyses.

Results: Models including BDQ-GS, BDQ-GDS or both variables combined discriminated similarly between groups. In contrast, models without time criterion or with 10 years' time criterion discriminated better than models including variables with 3 years' time criterion. These models discriminated highly (AUC = 85.98-87.78) between bvFTD and MDD and bvFTD and ADD, respectively.

Conclusion: BDQ-scores without any time criterion discriminated highly between early-stage bvFTD and non-bvFTD groups, which could improve the early diagnosis of bvFTD. With its standardised procedure, the BDQ is also appropriate for repeated assessments.

Keywords: Alzheimer’s disease; Behavioural disorder; Behavioural variant frontotemporal dementia; Depressive disorder; Questionnaire.

Fig. 1

Cut-offs between bvFTD and ADD patients. Percentages of patients with bvFTD who were correctly classified [sensitivity, orange line with triangles] and percentages of correctly classified ADD patients [specificity, blue line with circles] in relation to the BDQ-scores. Two cut-offs with either sensitivity or specificity above 90% are highlighted by dashed lines. The solid black line represents the optimal cut-off using the Youden-Index (sensitivity = 79%; specificity = 88%). bvFTD behavioural variant frontotemporal dementia, ADD Alzheimer’s disease dementia, BDQ Behavioural Dysfunction Questionnaire

Fig. 2

Cut-offs between bvFTD and MDD patients. Percentages of patients with bvFTD who were correctly classified [sensitivity, orange line with triangles] and percentages of correctly classified MDD patients [specificity, blue line with circles] in relation to the BDQ-scores. Two cut-offs with either sensitivity or specificity above 90% are highlighted by dashed lines. The solid black line represents the optimal cut-off using the Youden-Index (sensitivity = 76%; specificity = 78%). bvFTD behavioural variant frontotemporal dementia, MDD major depressive disorder, BDQ Behavioural Dysfunction Questionnaire