Objectives: Endoscopy remains mandatory in the diagnostic work-up of inflammatory bowel disease (IBD), but is a costly and invasive procedure. Identification of novel, noninvasive, diagnostic biomarkers remains a priority. The aim of the present study was to explore the potential of fecal amino acid composition as diagnostic biomarker for pediatric IBD.
Methods: In this case-control study, treatment-naïve, de novo pediatric patients with IBD from two tertiary centers were included. Endoscopic severity of ulcerative colitis (UC) and Crohn's disease (CD) was based on physician global assessment scores, substantiated by levels of fecal calprotectin and C-reactive protein at study inclusion. Patients were instructed to collect a fecal sample prior to bowel cleansing. Healthy controls (HCs) were recruited from primary schools in the same region. Dedicated amino acid analysis was performed on all samples.
Results: Significant differences between 30 IBD patients (15 UC, 15 CD) and 15 age and sex-matched HCs were found in six amino acids (histidine, tryptophan, phenylalanine, leucine, tyrosine, and valine; all area under the curve >0.75 and P < 0.005), displaying higher levels in IBD. When distributing the patients according to type of IBD, a similar spectrum of amino acids differed between UC and HC (histidine, tryptophan, phenylalanine, leucine, valine, and serine), whereas three amino acids were different between CD and HC (histidine, tryptophan, and phenylalanine).
Conclusions: Significantly increased levels of six different fecal amino acids were found in patients with IBD compared to controls. Whether these differences reflect decreased absorption or increased loss by inflamed intestines needs to be elucidated.