Diagnostic performance of Social Norms Questionnaire Italian version (SNQ-IT) for the early and differential diagnosis of dementia: the role of break and overadherence error patterns

Social norm knowledge is one of the main socio-cognitive facets that can be affected in neurocognitive patients. It includes understanding of social boundaries and adapting behavior according to the social context. Overadherence or violation of social norms characterize the cognitive profile of behavioral variant of frontotemporal dementia (bvFTD) patients. In this study, we explored social knowledge impairment patterns in a sample of patients with bvFTD compared to Alzheimer’s disease (AD) patients and healthy control subjects (HC), with the aim to define the diagnostic role of social norm deficits and the added value of the clinical error pattern analysis in the early and differential diagnosis of bvFTD. The Italian version of the Social norms questionnaire (SNQ-IT) was administered to 33 bvFTD, 20 AD and 20 HC. Global score (SNQgs), overadhere (SNQoes) and break (SNQbes) subscale scores were computed. Diagnostic performance of SNQgs, SNQoes and SNQbes scores were evaluated with the Receiver Operating Characteristic (ROC) curve analysis. A stepwise logistic regression model was applied to accurately classify bvFTD, including in the model only those variables found to be significant predictor variables. All scores significantly differed in bvFTD vs HC while SNQoes scores did not differ in bvFTD vs AD. SNQgs showed an excellent performance in differentiating bvFTD from AD (AUC 0.82). Logistic regression analysis identified SNQbes as the main variable, in combination with SNQgs, in accurately distinguishing bvFTD from HC and correctly classifying the 93% of patients. The combination of SNQbes and SNQgs was able to distinguish bvFTD from AD, correctly classifying the 90% of bvFTD patients. Knowledge of social norms is a crucial socio- cognitive subdomain early affected in bvFTD. SNQ-IT is a useful clinical tool for early diagnosis of bvFTD. Error pattern analysis may add crucial information for differential diagnosis identifying violations of social norms which are core signatures of social cognition changes in bvFTD.