Adaptation of the rheumatoid arthritis quality of life scale for Estonia

The aim of the study was to adapt the rheumatoid arthritis quality of life scale (RAQoL) for Estonia and assess its psychometric properties. The RAQoL was translated into Estonian using the dual panel method. The translation was assessed for face and content validity by means of interviews with 15 rheumatoid arthritis (RA) patients. Reproducibility and construct validity were estimated using a further sample of 50 patients. Unidimensionality of the final scale was assessed by Rasch analysis. No major problems occurred in translating the instrument, it was well accepted by interviewees. The Estonian RAQoL had good test-retest reliability, internal consistency and ability to discriminate between groups defined by patient-perceived severity. Predicted convergent and divergent validity was demonstrated. Unidimensionality of the instrument was confirmed by excellent fit to the Rasch model. The RAQoL is appropriate for use in clinical studies and trials involving RA patients.