A Validated Disease-Specific Symptom Index for Adults With Celiac Disease

Abstract

Although the incidence of celiac disease (CD) is increasing, studies have been hampered by the lack of validated outcome measures. We sought to create a disease-specific Celiac Symptom Index (CSI) to reliably assess relevant symptoms. A 36-item questionnaire was created after design by an expert committee and review/revision by patient focus groups. The survey, covering domains of CD-related symptoms and general health, was initially administered to 154 individuals with biopsy-proven CD; immunoglobulin (Ig)A tissue transglutaminase titers were determined, and gluten-free diet adherence was evaluated by a dietitian. The questionnaire was then revised to exclude questions with poor test characteristics and administered to a second, independent group of 52 individuals, to ensure validity. The subscales of "specific symptoms" and "general health" had excellent psychometric qualities that consisted of 11 and 5 items, respectively. The additive score based on these items was correlated with current general health, as measured by a visual analog scale and short form 36 general health subscale (P < or = .001 for both), as well as degree of adherence to the gluten-free diet (P = .008), lending external validity to the CSI. The resulting 16 questions make up the first CD-specific symptom index. The CSI allows for disease-specific monitoring of symptoms as an independent outcome measure or as part of a surrogate for disease activity in individuals with CD. The CSI might be an important tool for future clinical CD research.