Keitel Functional Test for patients with rheumatoid arthritis: translation, reliability, validity, and responsiveness.

BACKGROUND AND PURPOSE

The purpose of this study was to translate the German Keitel Functional Test (KFT) into Danish and test it for reliability, concurrent and predictive validity, and responsiveness in patients with rheumatoid arthritis (RA).

METHODS

Translation of the KFT was performed according to international recommendations, and the translated version was tested twice by 2 observers for intraobserver and interobserver reliability, with a 1-week interval between assessments, in 20 patients with RA with stable disease activity. Validity was investigated by studying 2 patient groups: (1) 15 patients with long-lasting (median=6 years) active RA, tested before and after 2, 6, and 14 weeks of anti-tumor necrosis factor alpha (TNF-alpha) inhibitor therapy, and (2) 35 patients with early (median=0.25 year) RA, tested at years 0, 0.5, 1, and 2. Twenty-three patients in the early RA group also were tested at year 7. KFT, conventional clinical and biochemical markers of disease activity, and Health Assessment Questionnaire (HAQ) were used.

RESULTS

The translated KFT showed good intraobserver reliability (intraclass correlation coefficients [ICC]=.90 and .95, coefficient of variation [CV]=3.5%) and interobserver reliability (ICC=.99 and .92, CV=3.5%), and the KFT correlated with several measures of disease activity and, most closely, with the HAQ. The KFT was, in contrast to clinical disease activity measures, not sensitive to changes over time. Only baseline KFT data were significantly related to functional changes over a long period of time as measured by the KFT, and only in the early RA group.

DISCUSSION AND CONCLUSION

The Danish translation of the KFT showed good reliability, acceptable concurrent validity, very poor responsiveness, and inconclusive results concerning predictive validity. The results of this study do not support the use of the KFT for monitoring function in clinical practice, as an outcome measure in clinical trials, or as a predictor of functional changes.