Objectives: To validate the systemic lupus activity questionnaire (SLAQ) in Spanish language.
Methods: The SLAQ questionnaire was translated and adapted in Spanish. Consecutive SLE patients from 8 centers in Argentina were included. A rheumatologist completed a Systemic Lupus Activity Measure (SLAM), Systemic Lupus Erythematosus Disease Activity Index (SLEDAI)-2K, and a physician's assessment. Reliability was assessed by internal consistency (Cronbach's alpha), stability by test-retest reliability (intraclass correlation coefficient), and construct validity by evaluating the correlation with clinically relevant scores. Sensitivity and specificity for clinically significant disease activity (SLEDAI ≥6) of different S-SLAQ cut-off points were evaluated.
Results: We included 97 patients ((93% female, mean age: 40 years (SD14.7)). Internal consistency was excellent (Cronbach's alpha = 0.84, p < 0.001), and the intraclass correlation coefficient was 0.95 (p < 0.001). Mean score of S-SLAQ was 8.2 (SD 7.31). Correlation of S-SLAQ was moderate with Patient NRS (r= 0.63 p< 0.001), weak with SLAM-no lab (r = 0.42, p <0.001) and SLAM (r = 0.38, p < 0.0001), and very weak with SLEDAI-2K (r = 0.15, p =0.1394). Using the S-SLAQ cutoff of five points, the sensitivity was 72.2% and specificity was 37.9%, for clinically significant disease activity.
Conclusions: The S-SLAQ showed good validity and reliability. A good correlation, similar to the original instrument, was observed with patient´s global disease activity. No correlation was found between S-SLAQ and gold standard disease activity measures like SLEDAI-2K and SLAM. The S-SLAQ cutoff point of 5 showed a good sensitivity to identify the active SLE population and therefore could be an appropriate screening instrument for disease activity in clinical and epidemiological studies.
Keywords: Systemic lupus erythematosus; disease activity; patient-self reported activity score; systemic lupus activity questionnaire.