Psychometric evaluation of a Brazilian Portuguese version of the Spitzer Quality of Life Index in patients with low back pain.

The purpose of this study was to adapt the Spitzer Quality of Life Index and evaluate its reliability in patients with low back pain. The following steps were followed: translation, back-translation, evaluation by a committee, and pretest. The reliability was estimated through stability and homogeneity assessment. The validity was tested comparing scores of the Spitzer (QLI) with the SF-36 and the Roland-Morris. The psychometric properties were evaluated by the self-application on 120 patients. Results showed that the Cronbach's Alpha was 0.77. Intraclass correlation coefficient for test-retest reliability was 0.960 (p<0.001; IC95%: 0.943; 0.972). Spearman s correlation coefficient for test-retest reliability was 0.937 (p<0.001). There was significant correlation between the Spitzer (QLI) scores and the dimensions of the SF-36. A significant negative correlation was found between the Spitzer (QLI) and the Roland-Morris scores (r = - 0.730). The adaptation process was conducted successfully and the questionnaire presented reliable psychometric measures.