Eosinophil Level Reporting and Interpretation

Standard Reporting Methods

Peak eosinophil counts in esophageal biopsies are expressed as absolute numbers per high-power field (hpf) or per 0.3 mm², with a diagnostic threshold for eosinophilic esophagitis of ≥15 eosinophils per 0.3 mm², representing an absolute count in the most densely populated field, as recommended by the British Society of Gastroenterology 1, 2, 3
Peripheral blood eosinophils are reported as absolute counts (cells/μL or ×10⁹/L), with normal absolute eosinophil counts ranging from 50-500 cells/μL, and blood eosinophilia defined by absolute thresholds (commonly >350-800 cells/μL depending on the reference) 4, 5

Absolute counts provide standardized, reproducible measurements that allow comparison across institutions and studies, and are used to monitor treatment response and guide biologic therapy decisions, with specific absolute thresholds (e.g., 150 cells/μL, 300 cells/μL) guiding decisions, according to the Journal of Allergy and Clinical Immunology 6, 7
Peak (maximum) counts are used rather than average counts when evaluating tissue eosinophilia, as inflammation is often patchy and focal, and the size of the measurement area significantly affects interpretation, with standardization to 0.3 mm² recommended to address historical variability in "high-power field" sizes across different microscopes 6, 7, 3

For esophageal biopsies, the peak absolute eosinophil count per 0.3 mm² from the most densely populated area should be reported, along with other histologic features, as recommended by the British Society of Gastroenterology 1, 3, 2
For peripheral blood, the absolute eosinophil count in cells/μL or ×10⁹/L should be reported, noting that 10-50% of patients with eosinophilic esophagitis may have elevated peripheral counts (typically modest 2-fold elevations), according to Gastroenterology 4