The reliability and validity of the Vertigo Symptom Scale and the Vertigo Dizziness Imbalance Questionnaires in a Turkish patient population with Benign Paroxysmal Positional Vertigo

The aim of this study was to adapt the Vertigo Symptom Scale (VSS) and the Vertigo Dizziness Imbalance (VDI) Questionnaires to the Turkish population and investigate the reliability and validity of the Turkish version. One hundred and three patients with Benign Paroxysmal Positional Vertigo (BPPV) were included in the study. The patients were evaluated with the VSS and the VDI twice, at recruitment and 24 hours later. To perform concurrent validity study study, patients were also assessed by the Beck Depression Inventory (BDI) and the Medical Outcomes Survey Short Form 36 (SF-36) which were formerly proved to be valid and reliable for use in Turkish population. The internal consistency of the VSS, VDI-symptom scale, and VDI-health-related quality of life scale were good with Cronbach's alpha of 0.91, 0.85, and 0.93 respectively which showed high reliability for the Turkish versions. Test-retest reliability was also good, with a high intraclass correlation coefficent (ICC) between the two time points; being 0.83 for the VSS, 0.90 for the VDI-symptom scale and 0.89 for the VDI-health related quality of life scale. Regarding concurrent validity, significant expected correlations were detected between the VSS and BDI (r = 0.55 p < 0.001) and the VSS and SF-36 (r = -0.43 p < 0.001). Significant low correlations were detected between the VDI-SS and BDI (r = 0.20 p < 0.05) and the VDI-SS and SF-36 (r = -0.21 p < 0.05). High correlations were observed between the VDI-HRQoL and BDI (r = -0.75 p < 0.001) and the VDI-HRQoL and SF-36 (r = 0.82, p < 0.001) which indicates high concurrent validity. The correlation between VDI-SS subscale scores and VDI-HRQoL subscale scores were 0.028 (P = 0.778) at the first time point. From the perspective of discriminant validity, it means that the VDI-SS measures a construct different from the one underlying the VDI-HRQoL. The adaptation of the VSS and VDI to the Turkish population was successful and both scales were found to be valid and reliable. Thus, they can be used in Turkish people with BPPV for assessment and monitoring the treatments. Besides, the results of the national studies in which these Turkish versions are used can be compared with those of the international studies.