Flexible sigmoidoscopy is required for the gold standard diagnostic technique for food protein-induced proctocolitis (FPIP) (FS). There is currently no approved, noninvasive test to confirm the diagnosis of FPIP. Eosinophil-derived neurotoxin (EDN), a byproduct of EOS degranulation, has been linked to eosinophilic infiltration in other tissues. The goal of this study was to compare EDN concentrations in rectal epithelium samples from babies with FPIP to those in a control population. Between July 2017 and May 2019, children who received regular FS at Arnold Palmer Hospital for Children were recruited in an IRB-approved, prospective, open-label pilot research. Rectal epithelial samples were collected using the following methods: rectal swab, cytology brushing through FS, and rectal biopsy through FS. Researchers next assessed EDN levels in the samples and compared them to levels reported in babies with FPIP and the control group. More than 60 EOS per 10 high-power fields (HPF) in rectal epithelial tissue acquired by rectosigmoid biopsy was classified as FPIP. A total of twenty-four patients were enrolled. Patients in the control group had normal histology, whereas those in the FPIP group had FPIP verified by biopsy. For both sample methods, rectal biopsy and rectal swab, EDN concentration was substantially greater in the FPIP group than in the control group.

EDN concentrations assessed from rectal swab and biopsy samples are increased, suggesting that it might be a helpful technique for screening for FPIP in children.

Reference: https://journals.lww.com/jpgn/Abstract/2020/10000/Using_Eosinophil_Biomarkers_From_Rectal_Epithelial.14.aspx