Open AccessValidation of the systemic lupus erythematosus activity questionnaire in a large observational cohort
Author(s) -
Yazdany Jinoos,
Yelin Edward H.,
Panopalis Pantelis,
Trupin Laura,
Julian Laura,
Katz Patricia P.
Publication year - 2008
Publication title -
arthritis care & research
Language(s) - English
Resource type - Journals
eISSN - 1529-0131
pISSN - 0004-3591
DOI - 10.1002/art.23238
Subject(s) - cronbach's alpha , construct validity , medicine , cohort , observational study , cohort study , physical therapy , reliability (semiconductor) , systemic lupus erythematosus , lupus erythematosus , disease , clinical psychology , psychometrics , immunology , power (physics) , physics , antibody , quantum mechanics
Objective To examine the reliability, construct validity, and responsiveness of the Systemic Lupus Erythematosus Activity Questionnaire (SLAQ) in a large observational cohort of persons with systemic lupus erythematosus (SLE). Methods We evaluated the reliability of the SLAQ using Cronbach's alpha and principal factor analysis and ascertained construct validity by studying the association of the SLAQ with other clinically relevant, validated patient assessments of health. We estimated responsiveness by calculating standardized response means and analyzing the association of changes in SLAQ scores with changes in other patient assessments of health. Results The SLAQ had excellent reliability, as reflected by Cronbach's alpha (0.87) and principal factor analysis (one factor accounted for 92% of the variance). SLAQ scores were strongly correlated with other health indices, including the Short Form 12 Physical Component Summary and the Short Form 36 Physical Functioning subscale. Scores were significantly higher for respondents reporting a flare, more disease activity, hospitalization in the last year, concurrent use of immunosuppressive medication, and work disability. The SLAQ demonstrated a small to moderate degree of responsiveness; standardized response means were 0.66 and −0.37 for those reporting clinical worsening and improvement, respectively. Across a range of other patient assessments of disease status, the SLAQ had a response in the direction predicted by these other measures. Conclusion The SLAQ demonstrates adequate reliability, construct validity, and responsiveness in our large, community‐based cohort and appears to represent a promising tool for studies of SLE outside the clinical setting.