Measuring illness behavior in patients with systemic sclerosis.

OBJECTIVE Illness behaviors (cognitive, affective, and behavioral reactions) among individuals with systemic sclerosis (SSc; scleroderma) are of clinical concern due to relationships between these behaviors and physical and mental quality of life, such as pain and symptoms of depression. Self-report measures with good psychometric properties can aid in the accurate assessment of illness behavior. The Illness Behavior Questionnaire (IBQ) was designed to measure abnormal illness behaviors; however, despite its longstanding use, there is disagreement regarding its subscales. The goal of the present study was to evaluate the validity of the IBQ in a cohort of patients with SSc. METHODS Patients with SSc (n = 278) completed the IBQ at enrollment into the Genetics Versus Environment in Scleroderma Outcome Study. Structural validity of previously derived factor solutions was investigated using confirmatory factor analysis. Exploratory factor analysis was utilized to derive SSc-specific subscales. RESULTS None of the previously derived structural models were supported for SSc patients. Exploratory factor analysis supported an SSc-specific factor structure with 5 subscales. Validity analyses suggested that the subscales were generally independent of disease severity, but were correlated with other health outcomes (i.e., fatigue, pain, disability, social support, and mental health). CONCLUSION The proposed subscales are recommended for use in SSc, and can be utilized to capture illness behavior that may be of clinical concern.