The development and validation of the vestibular activities and participation (VAP) measure for people with vestibular disorders based on the international classification of functioning, disability and health (ICF)

Background. Activities and participation domains are affected in people with vestibular disorders; however, specialized outcome measures for evaluating activities and participation according to the International Classification of Functioning, Disability and Health (ICF) do not exist.;Purpose. To develop and validate the Vestibular Activities and Participation (VAP) measure for people with vestibular disorders according to the ICF.;Methods. A list of activities and participation candidate items were generated and included in a survey. The survey was then sent to a panel of vestibular experts and agreement was obtained on the items to include in the VAP using the Delphi technique. The psychometric properties of the VAP were established including test-retest reliability; minimum detectable change at 95% confidence level (MDC95), concurrent validity with the World Health Organization Disability Assessment Schedule II (WHODAS II); convergent validity with the Dizziness Handicap Inventory (DHI), and discriminant validity. The test-retest reliability of the VAP total score was estimated using the Intra Class Correlation Coefficient (ICC), model (3,1) and the 95% confidence interval (CI). Agreement per-item was estimated using Cohen's kappa statistics. Concurrent and convergent validity were examined using the Spearman correlation coefficient (rho). Discriminant validity was established using a generalized linear model (GLM).;Results. Fifty five activities and participation items were generated in which 32 of them had 70% or greater agreement for inclusion in the VAP. The test-retest reliability of the VAP total score was excellent (ICC=.95), (CI=.91--.97). Un-weighted kappa (.41--.80) and weighted kappa (.58--.94) were good to excellent. The VAP had strong correlation (rho=.7, p<.05) with the WHODAS II and moderate to strong correlations (rho=.54--.74) with the DHI subscale and total scores. The MDC95 was .58. After adjustment for age, gender and self-reported imbalance were independent predictors of the transformed VAP total score.;Conclusion. The VAP measure was developed to examine the disabling effect of vestibular disorders on people's activities and participation based on the ICF. The VAP demonstrated excellent reliability and was validated with external instruments.