Higher Blood Eosinophil Counts During Acute Preschool Wheeze Are Associated With School‐Age Asthma: A Retrospective Cohort Study

ABSTRACT Aim To assess whether blood eosinophil counts (BEC) measured during acute preschool wheeze were associated with asthma after age five and added predictive information to clinical factors. Methods We reviewed the records of 1373 children aged 1–5, hospitalized for wheezing at a tertiary centre (2013–2024). Clinical predictors and BEC were obtained from the earliest available complete blood count during the index wheezing hospitalization. Respiratory outcomes were assessed for 323 children with available hospital and affiliated outpatient records after their fifth birthday. We used logistic regression and ROC analysis to assess whether BEC predicted later asthma. Results Persistent wheeze/asthma was identified in 115 children (35.6%). Median BEC was higher in children with persistent wheeze/asthma than in those without asthma (0.30 [0.10–0.66] vs. 0.14 [0.03–0.30] × 10 3 /μL; p < 0.001). BEC alone showed modest discrimination (AUC 0.673) and improved prediction when combined with five clinical predictors (AUC 0.789). A BEC threshold of 0.57 × 10 3 /μL identified a high‐specificity subgroup (sensitivity 30.4%, specificity 92.8%). Conclusion BECs during acute wheezing hospitalization were independently associated with later asthma and provided modest incremental predictive information when combined with clinical features. BEC may help identify hospitalized preschool children with wheeze who warrant closer follow‐up. External validation is required before clinical implementation.