The Challenge of IBD-Related Arthritis Screening Questionnaires in Early and Predominantly Entheseal Phenotypes

Introduction: Inflammatory bowel disease (IBD)-related arthritis is recognized as the most prevalent extraintestinal manifestation (EIM) of IBD. The objective of this study was to determine the prevalence and characteristics of undiagnosed IBD-related arthritis and to compare two screening questionnaires, DETection of Arthritis in Inflammatory boweL diseases (DETAIL) and IBd Identification of Spondyloarthritis Questionnaire (IBIS-q), for early disease detection. Methods: Between April and October 2023, both the DETAIL and IBIS-q questionnaires were administered to consecutive IBD outpatients visiting the University Hospital of Udine, Italy. During routine gastroenterology evaluations, patients aged > 18 years with Crohn’s disease (CD) or ulcerative colitis (UC) were requested to complete both questionnaires. Subsequently, all patients who completed the questionnaires underwent a blinded rheumatological evaluation within 2 weeks. Patients with a previous diagnosis of IBD-related SpA were then excluded. Results: Overall, 203 patients were enrolled, of whom 26 were excluded because of a prior diagnosis of inflammatory arthritis. Among the remaining 177 patients, 10/177 (5.6%) received a new diagnosis of IBD-related arthritis. The median duration of symptoms before diagnosis was 4 (IQR 1.8–10.5) months. Imaging-confirmed enthesitis was the predominant pattern in 8 out 10 cases (80%, with 8 out 8 lacking concomitant peripheral arthritis), axial involvement in 1 out 10 cases (10%), and peripheral arthritis in 1 out 10 cases (10%). The DETAIL questionnaire exhibited higher specificity, but lower sensitivity compared to the IBIS-q, with a sensitivity of 40.0% (12.2–73.8) and specificity of 84.4% (78.0–89.6) versus a sensitivity of 70.0% (34.8–93.3) and specificity of 74.3% (66.9–80.7). Both questionnaires performed less effectively than in other studies. Conclusion: This study highlights a significant proportion of undiagnosed IBD-related arthritis (5.6%). Enthesitis emerged as the predominant pattern of newly diagnosed arthritis in our cohort, likely due to the recent onset of symptoms. Our study underscores the importance of entheseal involvement in early IBD-related arthritis and the importance of incorporating entheseal involvement into screening questionnaires.