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.