Eosinophilias

Q: Hypereosinophilic syndromes (HES) is defined as absolute eosinophil count  AEC ≥1500/microL on two occasions (select one)

A) > 7 days apart

B) > 14 days apart

C) > 30 days apart

D) > 3 months apart

Answer: C

The objective of this question is to highlight the common misconceptions regarding the different definitions of eosinophilia. Conventionally, eosinophilia is defined as >5 percent of total WBC count. But merely looking at the percentage of the WBC may mislead a clinician. Eosinophilia is defined as AEC ≥500 eosinophils/microL. A clinician may have to calculate AEC by the following formula, as very high or low WBC count may change the value of AEC:

White blood cell (WBC) count/microL X percentage of eosinophils = AEC (eosinophils/microL) 

Also, there is a difference between eosinophilia, hypereosinophilia and hypereosinophilic syndromes (HES).

Eosinophilia is AEC ≥500 eosinophils/microL

Hypereosinophilia is ≥1500 eosinophils/microL 

Hypereosinophilic syndromes (HES) is AEC ≥1500/microL, on two occasions ≥30 days apart, plus at least one organ dysfunction attributable to eosinophilia. 

#hematology

#lab-medicine

References:

1. Tefferi A. Blood eosinophilia: a new paradigm in disease classification, diagnosis, and treatment. Mayo Clin Proc 2005; 80:75.

2.Roufosse F, Weller PF. Practical approach to the patient with hypereosinophilia. J Allergy Clin Immunol 2010; 126:39.

3. Klion A. Hypereosinophilic syndrome: current approach to diagnosis and treatment. Annu Rev Med 2009; 60:293.