Stiasny-Kolster et al. in 2007 developed the original German/English RBD Screening Questionnaire (RBDSQ) (Stiasny-Kolster et al., 2007). The RBDSQ is a 10-item patient self-rating instrument that assesses sleep behavior with short questions that have to be answered by either "yes" or "no" by the patient. Since patients do not always have a long-time companion, the bed partner's input was encouraged but not required. Items 1 to 4 address the frequency and content of dreams and their relationship to nocturnal movements and behavior. Item 5 asks about self-injuries and injuries of the bed partner. Item 6 consists of four subitems that assess nocturnal motor behavior more specifically, e.g., questions about nocturnal vocalization, sudden limb movements, complex movements, or items around the bed that fell down. Items 7 and 8 deal with nocturnal awakenings. Item 9 focuses on disturbed sleep in general and item 10 on the presence of any neurological disorder. The maximum total score for the RBDSQ is 13 points. The RBDSQ was applied to 54 RBD patients (mean age 53.7 years, range 19-79) who had been clinically diagnosed with iRBD (n=19), narcolepsy (n=33), early PD (n=2)) and 160 patients without RBD (age 50.8 years, range 20-83) who had been diagnosed as having RLS (n=73), narcolepsy (n=27), OSAS (n=21), hypersomnia (n=10), PLMD (n=8), insomnia (n=4), sleepwalking (n=4), epilepsy (n=3), nightmares (n=1), sleep bruxisum (n=1), or depression. (n=1). Also studied were 133 healthy subjects (mean age 46.9 years, range 20-72). Using a cut-off value of five points on the RBDSQ as a discriminatory variable, the questionnaire revealed a sensitivity of 96% and a specificity of 56%, correctly diagnosing 66% of subjects with sleep disorders. They mentioned that the lower specificity might be due to the fact that most of their control patients had sleep disturbances or neurological disorders that are known to be associated with periodic leg movements, e.g., RLS, PLMD, narcolepsy, and OSAS. This selection bias predisposed to positive answers for items that are related either to limb movements such as items 4, 5, 6.2, and 7 or to the presence of sleep and/or neurologic disorders such as for items 9 and 10, leading to higher RBDSQ total scores and thus to a lower specificity. Considering its high sensitivity, the RBDSQ represents an adequate tool to detect subjects with RBD. In subjects without additional neurologic or sleep disorders, the specificity was high, but in patients with either neurologic diseases or sleep disorders, the specificity is poorer but acceptable. The authors demonstrated the RBDSQ might be applied within a stepwise diagnostic process (questionnaire, interview, PSG).
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