To develop a rheumatoid hand disability scale in the Arabic language adapted for local sociocultural specificities and to test its psychometric properties.
The choice of hand activities was based on several published indices. The selected items were translated by the forward and backward translation procedures, several modifications were made, and after some questions were added, a provisional scale was obtained. In- and outpatients with rheumatoid arthritis (RA) according to the ACR criteria were chosen to answer the provisional scale and to assess the final scale. Impairment outcome measures (pain as measured on a visual analogue scale, morning stiffness, hand swelling, tenderness), and assessment of disability (on Lee's and Revel's functional indices) were also recorded. The intraclass correlation coefficient and the Bland and Altman methods were used to assess reliability. Construct (convergent and divergent) validity was investigated with use of Spearman's rank correlation, and a factor analysis was performed.
The provisional scale had 21 questions. The adaptation process left 10 questions about hand activity, with four levels of answers. Eighty patients with RA were recruited for the validation of the final scale. The intra- and interrater reliabilities of the scale were 0.96 and 0.94, respectively. Analysis by the Bland and Altman method showed no systematic trend. The scale had good construct validity, with expected convergence with Lee's functional index (r(s)=0.79) and Revel's functional index (r(s)=0.81) and divergence with age (r(s)=0.05), morning stiffness (r(s)=0.40), pain (r(s)=0.32), and tenderness (r(s)= -0.48). The factorial structure of the scale was satisfying, with two factors explaining 73% of the variance.
We developed an Arabic index that assesses hand disability due to RA and suits Tunisian people. Further studies are needed to confirm the validity of the scale in other Arabic countries.