Serum Eosinophilic Cationic Protein as a Useful Noninvasive Marker of Eosinophilic Gastrointestinal Disease in Children.

Purpose: Recently, the prevalence of eosinophilic gastrointestinal disease (EGID) has shown an increasing trend worldwide. As the diagnosis of EGID requires invasive endoscopy with biopsy, noninvasive markers for detecting EGID in suspected patients, particularly children, are urgently needed. Therefore, this study aimed to evaluate the diagnostic accuracy of serum eosinophil cationic protein (ECP) beyond peripheral eosinophil counts in pediatric patients with EGID.

Methods: Overall, 156 children diagnosed with EGID were enrolled and 150 children with functional abdominal pain disorder (FAPD) were recruited as controls. All participants underwent endoscopic biopsy in each segment of the gastrointestinal (GI) tract and serum ECP measurement, as well as peripheral eosinophil percent and absolute eosinophil count.

Results: Comparing EGID (n=156) with FAPD (n=150) patients, serum ECP levels were significantly higher in pediatric patients with EGID than in those with FAPD (25.8±28.6 µg/L vs. 19.5±21.0 µg/L, p=0.007), while there was no significant difference in peripheral eosinophil percent and absolute eosinophil counts between the two groups. Serum ECP levels were correlated with peripheral eosinophil percent (r=0.593, p<0.001) and the absolute eosinophil count (r=0.660, p<0.001). The optimal cutoff value of serum ECP for pediatric EGID was 10.5 µg/mL, with a sensitivity of 69.9% and a specificity of 43.4% with an area under the receiver operating characteristic curve of 0.562.

Conclusion: The combination of serum ECP levels and peripheral eosinophil counts, when employed with appropriated thresholds, could serve as a valuable noninvasive biomarker to distinguish between EGID and FAPD in pediatric patients manifesting GI symptoms.