Reliability and validity of the university of california, los angeles scleroderma clinical trial consortium gastrointestinal tract instrument

Abstract

OBJECTIVE: To refine the previously developed scleroderma (systemic sclerosis [SSc]) gastrointestinal tract (GIT) instrument (SSC-GIT 1.0). METHODS: We administered the SSC-GIT 1.0 and the Short Form 36 to 152 patients with SSc; 1 item was added to the SSC-GIT 1.0 to assess rectal incontinence. In addition, subjects completed a rating of the severity of their GIT involvement (from very mild to very severe). Evaluation of psychometric properties included internal consistency reliability, test-retest reliability (mean time interval 1.1 weeks), and multitrait scaling analysis. RESULTS: Study participants were mostly women (84%) and white (81%); 55% had diffuse SSc. Self-rated severity of GIT involvement ranged from no symptoms to very mild (39%), mild (21%), moderate (31%), and severe/very severe (9%). Of an initial 53 items in the SSC-GIT 1.0, 19 items were excluded, leaving a 34-item revised instrument (the University of California, Los Angeles Scleroderma Clinical Trial Consortium GIT 2.0 [UCLA SCTC GIT 2.0]). Analyses supported 7 multi-item scales: reflux, distention/bloating, diarrhea, fecal soilage, constipation, emotional well-being, and social functioning. Test-retest reliability estimates were >/=0.68 and coefficient alphas were >/=0.67. Participants who rated their GIT disease as mild had lower scores on a 0-3 scale on all 7 scales. Symptom scales were also able to discriminate subjects with corresponding clinical GIT diagnoses. The Total GIT Score, developed by averaging 6 of 7 scales (excluding constipation), was reliable and provided greater discrimination between mild, moderate, and severe self-rated GIT involvement than individual scales. CONCLUSION: This study provides support for the reliability and validity of the UCLA SCTC GIT 2.0, an improvement over the SSC-GIT 1.0, and supports a Total GIT Score in SSc patients with GIT.