Construct validity and responsiveness of the vertigo symptom scale-short form in patients with chronic dizziness

BackgroundThe Vertigo Symptom Scale-Short Form (VSS-SF) is commonly used in clinical vestibular research but its ability to serve as an outcome measure has not been investigated.ObjectivesTo examine construct validity and responsiveness of the total scale and subscales addressing autonomic-anxiety (VSS-A) and vertigo-imbalance (VSS-V) in individuals with chronic dizziness.MethodsCross-sectional and longitudinal designs were applied. Predefined hypotheses were defined about the relationship between scores and change scores of the VSS-SF, VSS-V and VSS-A, assessing perceived symptoms of dizziness, and respective scores of other instruments assessing similar constructs, requiring 75% of hypothesis confirmed. The ability to discriminate between perceived improvement and not improvement by change scores was also examined.Major findingsThe VSS-SF demonstrated satisfactory construct validity with 75% of hypotheses confirmed, but not sufficient responsiveness with only 67% of hypotheses confirmed. Only the VSS-V showed adequate responsiveness to change by area under the ROC curve= 0.72. The optimal cut-off value to classify between improved and not improved patients was 4.5 on the 0-32-point scale.ConclusionsThe VSS-SF and subscales demonstrated acceptable construct validity supporting its clinical use. More studies on responsiveness are needed before a conclusion can be drawn regarding their ability to serve as an outcome measure.