Cross-cultural adaptation of a brief outcome questionnaire for Spanish-speaking arthritis patients

Objective. To cross-culturally adapt a brief self-assessment questionnaire to measure outcome among English- or Spanish-speaking patients with arthritis. Methods. A questionnaire containing the following items was translated to Spanish: the 8 activities of daily living (ADL) questions of the Modified Health Assessment Questionnaire; a question about the duration of morning stiffness; and a 10-point pain scale. Equivalence to the original English, test-retest reliability, and construct, criterion, and discriminant validity were determined on a population of patients from 4 clinical centers. Results. English-Spanish equivalence and test-retest reliability of the questionnaire were almost perfect (intra-class correlation coefficients [r_i] ≥0.90 for each). Construct validity, measured by comparing questionnaire scores with an occupational therapist's evaluation, was also near-perfect in both languages (r_i = 0.93 for English and 0.89 for Spanish). Both versions of the questionnaire correlated well with the physician-determined Steinbrocker functional class, as well as with the amount of pain, grip strength, and walking velocity. Patients with systemic lupus erythematosus, rheumatoid arthritis, osteoarthritis, and fibromyalgia differed significantly in their pain:ADL ratios, in both languages. Conclusion. The items of the Spanish questionnaire that we have adapted are equivalent to the original English versions. This questionnaire is suitable for studying Spanish-speaking subjects with arthritis in the US and elsewhere.