Development of a Preliminary Scleroderma Gastrointestinal Tract 1.0 Quality of Life Instrument
Published in: Arthritis Care and Research, v. 57, no. 7, Sep. 28, 2007, p. 1280-1286
Posted on RAND.org on January 01, 2007
OBJECTIVE: Gastrointestinal tract (GIT) involvement occurs in 90% of patients with systemic sclerosis (SSc) and has a major impact on health-related quality of life (HRQOL). The authors developed an HRQOL instrument for persons with SSc. METHODS: The Scleroderma Gastrointestinal Tract 1.0 (SSC-GIT 1.0) survey was developed after an extensive literature search, solicitation and consideration of experts' opinions, and 2 focus groups of 16 subjects with SSc and GIT involvement. A 75-item, self-reported measure assessing bowel involvement, emotional well-being, and social functioning was administered to subjects with SSc and GIT involvement. Also, subjects completed the Short Form 36 and rated the severity of their GIT symptoms (very mild to very severe), and items were transformed linearly to a scale with a possible range of 0 (worse health) to 100 (better health). Evaluation of psychometric properties included internal consistency reliability, test-retest reliability (1.3-week median time interval), multitrait scaling analysis, and exploratory factor analysis. RESULTS: Study participants (n = 88) were primarily female (95.5%), white (79.3%), and had a mean age of 52.4 years. Self-rated severity of GIT involvement ranged from very mild or mild (36.0%) to moderate (44.0%) to severe or very severe (20.0%). Of 75 items, 23 had low item-total correlations ( 0.39) and were excluded, leaving a 52-item instrument. Analyses supported 6 multi-item HRQOL scales: reflux/indigestion, diarrhea, constipation, pain, emotional well-being, and social functioning. Test-retest reliability estimates ranged 0.69-0.90 and Cronbach's alpha ranged 0.69-0.93. Participants who rated their GIT disease as mild had the highest scores (better health) on all 6 scales; participants who rated their GIT as severe had the lowest scores (poor health). CONCLUSION: The results support the reliability and validity of the SSC-GIT 1.0 as a measure of SSc GIT involvement. Further research is needed to examine the ability to detect change over time and define minimally important differences.