Objective: To assess whether the functional disability in Japanese patients with systemic sclerosis (SSc) can be adequately evaluated by the Health Assessment Questionnaire (HAQ) developed in the United States.
Methods: The HAQ was completed by 121 Japanese patients with SSc, in whom SSc-specific physical examinations and laboratory tests were performed at the same time. Clinical findings associated with the disability index (DI) and individual components of the HAQ were examined using Student's t tests and Pearson's correlation tests. Logistic regression analysis was used to identify clinical findings that independently contributed to the increase in the HAQ-DI score.
Results: Japanese patients with SSc had significant functional disability, especially in the categories of eating and gripping, but the degree of disability was much less than was reported in previous studies carried out in the US. The increase in the HAQ-DI score was strongly correlated with increased total skin score, reduced oral aperture, reduced hand extension, increased finger flexion, subcutaneous calcinosis, flexion contractures, increased erythrocyte sedimentation rates, decreased percent vital capacity, and vascular involvement (p < 0.001 for all correlations). Multivariate logistic regression analysis showed that hand extension was the most important and an independent correlate of the HAQ-DI.
Conclusion: Our multicenter, cross-sectional study has demonstrated that the self-administered HAQ is a valuable assessment tool of functional disability in Japanese SSc patients, who have social customs different from Americans, but functional disability measured by the HAQ is potentially influenced by ethnic variability.