Eosinophilic esophagitis: absolute eosinophilic count, peak eosinophilic count, and potential biomarkers of eosinophilic degranulation products-an in-depth systematic review.

Background: Eosinophilic esophagitis is a chronic inflammatory disorder, often relapsing. There is an increasing need to develop new alternative diagnostic and monitoring methods on a critical basis, which will provide samples through none or minimally invasive procedures. This study aims to identify and document the types and roles of potential biomarkers in eosinophilic esophagitis released by eosinophils as well as the potential relationship to the peak eosinophilic count and the degree of degranulation of eosinophils (DGE/DGE + NDGE: degranulated eosinophils/degranulated eosinophils and non-degranulated eosinophils).

Methods: This is the first in-depth systematic review study using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) parameters involving a literature search of academic databases (PubMed, Scopus, Medline, Google Scholar, and Cochrane Database, 2011-2022) targeting specifically the eosinophilic counts and ratio, and the eosinophilic degranulation products as potential biomarkers. Data were extracted from ten selected studies and presented on a spreadsheet.

Results: The studies show the ability to detect eosinophilic and non-eosinophilic degranulation products, and absolute eosinophilic count in samples, including blood and urine, thereby serving as potential surrogates in making the diagnosis or monitoring disease progression in the future. There is an obvious paucity of studies that correlate potential biomarkers to the degree of degranulation of eosinophils.

Conclusions: A few minimally invasive methods and biomarkers may be suggested as alternative tools in diagnosing and monitoring eosinophilic esophagitis. While there is no consensus on the clinical usefulness of these biomarkers, our critical evaluation may suggest that the eosinophilic degranulation ratio (DGE/DGE + NDGE: degranulated eosinophils/degranulated eosinophils and non-degranulated eosinophils) in the esophagus may be critical for evaluating properly these biomarkers. An increasing trend may culminate in the potential clinical use of these biomarkers evaluated not only with the peak eosinophilic count, but also with the degranulation score upon regulatory bodies' approval to monitor eosinophilic esophagitis in the future. We strongly advocate for the necessity to score the esophageal biopsies with both a peak eosinophilic count and a score of the degranulated eosinophils.