Validity and reliability of the Turkish version of the Innsbruck RBD-9 diagnostic inventory (IRBD-9-TR)

Isolated rapid eye movement (REM) sleep behavior disorder (iRBD) is characterized by loss of the normal atonia of REM sleep accompanied by repetitive motor and behavior phenomena of dream content.

To evaluate the reliability and validity of the Turkish version of the original form of the Innsbruck Rapid Eye Movement Sleep Behavior Disorder Diagnostic Inventory (IRBD-9) scale (IRBD-9-TR) and ensure that this screening test can be easily used in the Turkish language.

The present is a multicenter and prospective study involving 184 patients: 51 with iRBD and 133 healthy controls. The iRBD patients were not diagnosed before submitted to video polysomnography (vPSG) and filling out the IRBD-9-TR.

The optimal cut-off value for the IRBD-9-TR symptom score was of 0.28, with a sensitivity of 0.941 and a specificity of 0.947, and 94.4% of the patients were correctly diagnosed. The rotated factor loadings for the diagnostic accuracy of each individual question showed that the short version of the IRBD-9-TR (questions 1, 2, 3, 6, and 8) presented higher specificity and excellent discrimination of iRBD patients from healthy controls. The Cronbach's α coefficient for the symptom section of the IRBD-9-TR was of 0.857, and the Kappa coefficient, of 0.885.

The short version of the IRBD-9-TR presents good validity and reliability to be used as a screening test to assess iRBD patients. It is convenient and potentially useful in both outpatient clinical and epidemiologic research settings.