To assess the usefulness of hand function measurements in a study of treatment effects of tumour necrosis factor (TNF) blockers and to define the relationship between different hand function tests and also relate hand function to general disability and disease activity.
The study group consisted of 49 patients with established rheumatoid arthritis (RA) who were followed for 1 year while on TNF inhibitors. Evaluation of hand function included Signals of Functional Impairment (SOFI), grip and pinch grip force, and the Grip Ability Test (GAT). General disability was assessed by the Health Assessment Questionnaire (HAQ) and disease activity by the 28-joint Disease Activity Score (DAS28). The standardized mean response (SMR) method was used to evaluate sensitivity to change for all hand tests using DAS28 and HAQ as external indicators of change.
HAQ, DAS28, grip and pinch grip force, and GAT showed a highly significant improvement over time (p<0.001). The improvement in SOFI was also significant (p<0.01). The correlations between the different hand tests varied between 0.45 and 0.72. All hand function tests were significantly related to HAQ but showed only weak correlations to DAS28. SOFI, grip force, and pinch grip force showed large sensitivity for improvement in DAS28 and HAQ (SMR = 0.8-0.9). GAT showed modest sensitivity (SMR = 0.6-0.7).
Patients with advanced RA attained considerable improvement in hand function that was only partly reflected by measures of general disability and disease activity. Focused assessment of hand function is therefore important for optimal evaluation of treatment response.