Interobserver reliability of ICSD-R criteria for REM sleep behaviour disorder

We estimated the interobserver reliability (IR) of the diagnosis of rapid eye movement (REM) Sleep Behaviour Disorder (RBD) among trained neurologists, with the application of International Classification of Sleep Disorders Revised (ICSD-R), by means of videotaped interviews of people with motor sleep behaviour disorders of different nature. IR of clinical judgement for the diagnosis of RBD was "substantial" (Kappa 0.65); nevertheless, some criteria ('limb or body movement associated with dream mentation', criterion B, and 'sleep behaviours (that) disrupt sleep continuity', criterion C3) showed a 'moderate' IR, resulting from the intrinsic limitations of the patient report and terminological ambiguity. Further clarification of terminology of the ICSD-R criteria would be useful to improve the reliability.