An English and Spanish quality of life measure for rheumatoid arthritis.

OBJECTIVE: To develop a rheumatoid arthritis-specific health-related quality of life instrument, translate the English instrument into Spanish, and test the scaling assumptions, reliability, validity, and feasibility of both the English and Spanish versions.

METHODS: The development of the Quality of Life-Rheumatoid Arthritis Scale (QOL-RA Scale) involved literature review, consultations with experts, 40 face-to-face interviews, and 5 focus group discussions with multiethnic and multilingual women with rheumatoid arthritis (RA). Translation design facilitated conceptual and linguistic equivalence. Data for the psychometrics came from telephone interviews of a sample of 107 Caucasian/English and 80 Hispanic/Spanish women with RA. The instruments were (a) the Arthritis Impact Measurement Scales 2 (AIMS2), (b) the Lubben Social Network Scale (LSNS), (c) the Center for Epidemiologic Studies-Depression Scale (CES-D), and (d) the QOL-RA Scale. Descriptive statistics, significance tests, Cronbach's alpha technique, correlation, and factor analysis were used.

RESULTS: The QOL-RA Scale, an 8-item scale, took 2 to 3 minutes to administer. Psychometric analysis revealed that the psychometric attributes and constructs of both English and Spanish questionnaires are comparable (i.e., equivalent). Both versions demonstrated the following: (a) normal distribution of the QOL-RA Scale, roughly symmetrical distributions of the items, equivalent means and standard deviations across items, and less than 10% floor and ceiling effects, (b) Cronbach's alpha coefficients of 0.87-0.90, (c) significant correlations of the QOL-RA Scale with the AIMS2 subscales, LSNS, and CES-D, ranging from 0.25 to 0.66 (P < or = 0.01), and (d) extraction of 2 factors, namely physio-psychological and socio-psychological, that explained 65% to 73% of the variance in the scale scores.

CONCLUSION: The QOL-RA Scale, in both English and Spanish versions, appears to meet the assumptions of a summated rating scale and the criteria of relevance, reliability, validity, feasibility, and adaptability to several languages.