Proteomic Discovery of Stool Protein Biomarkers for Distinguishing Pediatric Inflammatory Bowel Disease Flares.

Fecal calprotectin, the heterodimer of S100A8/S100A9, makes up ∼60% of neutrophil cytoplasmic protein content and is a canonical clinical biomarker of gut inflammation. Fecal calprotectin is commonly used to diagnose inflammatory bowel disease (IBD) and has an average sensitivity of 93% and specificity of 96%. For diagnosing pediatric IBD, calprotectin fecal tests have similar sensitivity (92%) but substantially less specificity (76%). Low specificity, especially in pediatric patients, means a high likelihood of false negative diagnoses, suggesting that a substantial number of active IBD cases remain undiagnosed and untreated. To improve on calprotectin as an effective IBD monitoring tool in pediatric populations, specificity must be increased. To develop an assay with higher specificity in pediatric patients, we identified a panel of multiple proteins that are present in both IBD flare and remission but have distinct abundance ranges between each condition. From a pilot cohort of 10 pediatric patients in states of either active disease or remission, we discovered and relatively quantified hundreds of stool proteins. Of these, our mass spectrometry-based study prioritized at least 5 that have potential to augment negative predictive power of mucosal-level inflammation alongside fecal biomarkers such as calprotectin.