Relationship between self-reported disability and functional capacity in patients with Whiplash Associated Disorder

Purpose Patients with chronic Whiplash Associated Disorders (WAD) report symptoms and disability. Neither the relationship between self-reported disability and functional capacity, nor its predictors have been investigated in patients with WAD. This was the purpose of this study. Method This was a cross-sectional study. Participants were patients with WAD on sick leave. Self-reported disability was assessed with the Neck Disability Index (NDI). Functional capacity was assessed with a six-item neck functional capacity evaluation (FCE). Correlation coefficients were used to express the relationship between NDI (total and items) and FCE. Multivariate linear regression analyses were performed to identify independent predictors of NDI and FCE. Results Forty patients were measured, of whom 18 (45 %) were male. Mean age was 33 years, median duration of complaints was 12 months, and 75 % had a pending insurance claim. Correlations between NDI and FCE tests varied from -0.39 to -0.70. Independent predictors of NDI were pain intensity and a pending claim, explaining 43 % of the variance. Independent predictors of FCE were NDI, gender, and pain intensity, explaining 20-55 % of the variance. Conclusions Self-reported disability and functional capacity are related but different. Both can part be predicted by pain intensity. A pending claim can predict higher self-reported disability. Both constructs are complementary and are recommended to determine disability in patients with WAD comprehensively.