Redefining Hematology Referral Thresholds for Eosinophilia.

Area of Science:

• Hematology
• Clinical Pathology

Background:

• Eosinophilia is a frequent laboratory finding necessitating hematologic evaluation.
• The clinical utility of hematology consultations for eosinophilia is not well-defined.
• Stratification and diagnosis spectrum for eosinophilia require further characterization.

Purpose of the Study:

• To refine stratification criteria for eosinophilia.
• To characterize the range of diagnoses associated with eosinophilia.
• To evaluate the predictive value of absolute eosinophil count (AEC) for clinically meaningful outcomes.

Main Methods:

• Retrospective study of 142 patients referred for hematology evaluation due to eosinophilia (AEC ≥ 0.5 × 10^9/L).
• Analysis of patient diagnoses, including idiopathic eosinophilia, hypereosinophilic syndrome (HES), and secondary causes.
• Receiver operating characteristic (ROC) analysis to determine the predictive accuracy of AEC for significant eosinophilia.

Main Results:

• Idiopathic eosinophilia was observed in 44.8% of patients.
• Hypereosinophilic syndrome (HES) was diagnosed in 20.3% of cases.
• Identifiable secondary causes included asthma (9.8%), parasitic infection (7.7%), autoimmune disease (4.9%), and drug reactions (4.9%).
• An AEC threshold of 1.5 × 10^9/L demonstrated 97% sensitivity for predicting HES or the need for eosinophilia-specific therapy.

Conclusions:

• An absolute eosinophil count (AEC) threshold of 1.5 × 10^9/L or higher may warrant hematology referral.
• This threshold is particularly relevant for low-risk and asymptomatic patients.
• External validation of this proposed referral threshold is recommended.