Urinary Hydroxyproline as an Inflammation-Independent Biomarker of Inflammatory Bowel Disease

Abstract

Predicting responses and monitoring the severity of inflammatory bowel disease (IBD) is challenging due to a lack of specific biomarkers. This study identifies urinary hydroxyproline, a marker of collagen turnover elevated in experimental colitis, as independent of conventional biomarkers like creatinine, glomerular filtration rate, C-reactive protein, and fecal calprotectin. Among 71 IBD patients, urinary hydroxyproline levels were significantly higher compared with 36 controls, with an area under the receiver operating characteristic curve of 0.814, highlighting its potential as a diagnostic tool. No significant difference in hydroxyproline levels was observed between the 50 Crohn’s disease and 21 ulcerative colitis patients, nor was there a correlation with kidney function markers, gastrointestinal symptom severity, or stool consistency. Disease localization was not associated with urinary hydroxyproline levels. Interestingly, 14 patients with primary sclerosing cholangitis and IBD also exhibited elevated urinary hydroxyproline levels, comparable to IBD patients but higher than healthy controls. This underscores the role of urinary hydroxyproline as an independent biomarker for IBD diagnosis, without association with disease severity or established markers like fecal calprotectin.