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.