Psychometric properties of the Vertigo symptom scale – Short form

Kjersti Wilhelmsen^*¹^,2 , Liv Inger Strand^*¹^,3 , Stein Helge G Nordahl² , Geir Egil Eide⁴ and Anne Elisabeth Ljunggren¹

¹Department of Public Health and Primary Health Care, Section for Physiotherapy Science, University of Bergen, Norway

²National Centre for Vestibular Disorders, Department of Otorhinolaryngology/Head and Neck Surgery, Haukeland University Hospital, Bergen, Norway

³Department of Physical Therapy, Haukeland University Hospital, Bergen, Norway

⁴Centre for Clinical Research, Haukeland University Hospital, and Department of Public Health and Primary Health Care, University of Bergen, Norway

author email corresponding author email* Contributed equally

BMC Ear, Nose and Throat Disorders 2008, 8:2doi:10.1186/1472-6815-8-2


Published:	27 March 2008

Abstract

Background

The aim of the study was to examine the psychometric properties of the Vertigo symptom scale – short form (VSS-SF), a condition-specific measure of dizziness, following translation of the scale into Norwegian.

Methods

A cross-sectional survey design was used to examine the factor structure, internal consistency and discriminative ability (sample I, n = 503). A cross-sectional pre-intervention design was used to examine the construct validity (sample II, n = 36) of the measure and a test-retest design was used to examine reliability (sub-sample of sample II, n = 28).

Results

The scree plot indicated a two factor structure accounting respectively for 41% and 12% of the variance prior to rotation. The factors were related to vertigo-balance (VSS-V) and autonomic-anxiety (VSS-A). Twelve of the items loaded clearly on either of the two dimensions, while three items cross-loaded. Internal consistency of the VSS-SF was high (alpha = 0.90). Construct validity was indicated by correlation between path length registered by platform posturography and the VSS-V (r = 0.52), but not with the VSS-A. The ability to discriminate between dizzy and not dizzy patients was excellent for the VSS-SF and sub-dimension VSS-V (area under the curve 0.87 and 0.91, respectively), and acceptable for the sub-dimension VSS-A (area under the curve 0.77). High test-retest reliability was demonstrated (ICC VSS-SF: 0.88, VSS-V: 0.90, VSS-A: 0.90) and no systematic change was observed in the scores from test to retest after 2 days.

Conclusion

Using a Norwegian translated version of the VSS-SF, this is the first study to provide evidence of the construct validity of this instrument demonstrating a stable two factor structure of the scale, and the identified sub-dimensions of dizziness were related to vertigo-balance and autonomic-anxiety, respectively. Evidence regarding a physical construct underlying the vertigo-balance sub-scale was provided. Satisfactory internal consistency was indicated, and the discriminative ability of the instruments was demonstrated. The instrument showed satisfactory test-retest reliability.