Validation of the UCLA Scleroderma Clinica Trial Gastrointestinal Tract Instrument version 2.0 for systemic sclerosis

The University of California at Los Angeles (UCLA) Scleroderma Clinical Trial Consortium GI Tract Instrument (UCLA SCTC GITI) was recently developed to measure gastrointestinal tract disease in systemic sclerosis (SSc). Our study assesses the internal consistency and validity of the instrument in a different population than was used in the original study.

A sample of 113 consecutive patients with SSc from the Canadian Scleroderma Research Group (CSRG) Registry completed the UCLA SCTC GITI, a self-administered questionnaire with 7 scales and an overall score. Reliability was evaluated using Cronbach's alpha coefficient and validity was determined by testing multiple constructs.

Our subjects were slightly older than the original cohort, and had less formal education and less diffuse cutaneous disease. The overall score of the instrument correlated well with the GI scale of the Health Assessment Questionnaire for the Spondyloarthropathies (GI-S-HAQ; r = 0.58, p < 0.001) and the total number of GI symptoms (r = 0.77, p < 0.001). Each subscale correlated well with the GI-S-HAQ. The individual scales and the overall score were able to differentiate between categorical groupings of the GI-S-HAQ. The scale scores differentiated well those patients with clinical involvement of the corresponding GI problem. Multiple linear regression adjusting for age, disease duration, sex, and ethnicity showed that the UCLA SCTC GITI had a significant association with both the physical component summary and the mental component summary of the Medical Outcomes Study Short-Form 36 questionnaire.

Our study confirms that the UCLA SCTC GITI version 2.0 will be a useful tool for assessing the role of GI involvement in SSc, even in a population with substantially different characteristics than the subjects originally tested.