Underestimation of airway luminal eosinophilia by quantitative sputum cytometry

Abstract Rationale On Wright-stained sputum cytospins, eosinophil differential of ≥ 1.2% is considered abnormal, and 2.3% identifies an eosinophilic endotype. We hypothesized that failure to consider free granules (FEG), the re-emergence (unmasking) eosinophilia due various reasons underestimate prevalence Methods This a retrospective analysis our Institutional Review Board-approved clinical database. Of 24,176 examinations sputa from patients with airway diseases, 17,693 were viable cell counts 9570 (6604 on single occasion, 2967 multiple occasions). The intact % at 1.2 thresholds was first examined. Then, additional evidence assessed by semi-quantitative enumeration FEGs. In those whose examined occasions (at time exacerbation or after corticosteroid dose reduced), . Results Using threshold 1.2%, 6289/17693 (35.6%) classified as eosinophilic. increased 7850/17693 (44.4%) when presence FEGs considered. 2.3%, 4647/17693 (26.3%) 5435/17693 (30.7%) FEG Extrapolating observed in who had whole sample, we estimated would be least 60% samples, clinically relevant 48.5% samples. Conclusions large cytometry database (17,693 counts), demonstrate point count underestimates variety diseases. increases 35.6 (40% underestimation) threshold, 26.3 (45% second examination are has important implications identify Th2 high endotype both for trials anti-eosinophil therapies, select may respond well glucocorticosteroids anti-IL5 therapies.