National validation and proposed revision of REM sleep behavior disorder screening questionnaire (RBDSQ)

We validated the Italian version of the rapid eye movement sleep behavior disorder (RBD) screening questionnaire (RBDSQ) and calculated its cut-off value for discriminating RBD group from other sleep disorders and healthy controls (HC). 380 patients with sleep disorders and 101 HC were enrolled. RBDSQ achieved an acceptable Cronbach's α value of 0.787 and item 10 was the only one with a very low item-total biserial correlation (0.141). At ROC analysis, we obtained an AUC of 0.888, denoting a good performance of the RBDSQ total score for predicting the RBD status. The optimal cut-off value was 8 and it achieved good values of both sensitivity and specificity (0.842 and 0.780, respectively). Due to the poor performance of item 10 in our sample, we analyzed the RBDSQ without this item (called "revised RBDSQ"). We obtained a good Cronbach's α of 0.802. When evaluating the performance of the revised score in predicting the RBD status, we obtained an increased value of AUC (0.899). The optimal cut-off value was still 8 (sensitivity = 0.829; specificity = 0.820). The Italian version of RBDSQ is a sensitive tool for the identification of RBD patients. An improvement of the instrument could be obtained by removing item 10 and define a higher cut-off value of 8. The "revised RBDSQ" represents a reliable screening questionnaire for primary care physicians and neurologists and its employment may facilitate the choice of subjects that should undergo a PSG that confirms the diagnosis of RBD, thus avoiding polysomnographic exams when not needed.