Objective: To validate a cross-culturally translated and adapted Dutch version of the Functional Index for Hand Osteoarthritis (FIHOA) in patients with osteoarthritis (OA) of the hands and to evaluate its construct validity by comparing with the Australian/Canadian Osteoarthritis Hand Index (AUSCAN).
Methods: The FIHOA was translated into Dutch and cross-culturally adapted. The questionnaire was administered to 72 patients with hand OA (female/male ratio: 64/8, handedness: right: 62/left: 7/both: 3). A visual analogue scale (VAS) pain scale (100mm) and the AUSCAN questionnaire were also recorded. An item-item analysis was performed. Test-retest reliability (time interval: 5 days) was assessed in 21 patients with intraclass correlation coefficient (ICC) and Bland and Altman graphical method. Construct validity was assessed by Spearman rank correlation coefficient between the FIHOA and AUSCAN.
Results: Internal consistency was high (Cronbach's alpha=0.89). All items, except for one ('Are you able to clench the fist?'), and the mean total FIHOA scores were statistically different between the subgroups based on the VAS (mean total score=7.46 and 14.19, in a-/mild symptomatic and symptomatic group, respectively (P<0.001)). The Spearman's correlation between all subscales of the AUSCAN (pain, stiffness, functionality) and the FIHOA was good, especially with the subscale functionality (r=0.81, P<0.01). Test-retest reliability was excellent with an ICC of 0.96 for the total score and the Bland and Altman plot showing a homogeneous distribution of the differences.
Conclusion: The psychometric properties of the Dutch version of the FIHOA are excellent. There is a good correlation between the FIHOA and all subscales of the AUSCAN, especially the subscale functionality.