Defining Neutropenia

Q: Neutropenia is defined as an absolute neutrophil count (ANC) of less than? -select one

A) 500/microL

B) 1500/microL

Answer: B

Neutropenia is defined as an absolute neutrophil count (ANC) of less than 1500/microL. The formula to calculate ANC is 

ANC = WBC (cells/microL) x percent (PMNs + bands) ÷ 100

Where:

WBC = white blood cell count

PMNs = polymorphonuclear cells 

There are various online calculators available.

An ANC below 500 cells/L (choice B) does not define ANC, but at this level, the risk of infection is very high.

The general rule of thumb suggests that if ANC:

• 1000 to 1500/microL = No significant risk of infection; fever can be managed on an outpatient basis
• 500 to 999/microL = Some risk of infection; fever can occasionally be managed on an outpatient basis
• 200 to 499/microL = Significant risk of infection; fever should always be managed on an inpatient basis with parenteral antibiotics, despite few clinical signs of infection
• less than 200/microL = Very significant risk of infection; fever should always be managed on an inpatient basis with parenteral antibiotics, despite few or no clinical signs of infection

The objective of the above question is to identify the common mistakes clinicians make while defining neutropenia.

References:

1. Min KI, Byeon S. Diagnosis and management of neutropenia. Blood Res. 2025 May 26;60(1):30. doi: 10.1007/s44313-025-00079-1. PMID: 40418265; PMCID: PMC12106181.

2. Patel S. Calculated decisions: Absolute neutrophil count. Emerg Med Pract. 2018 Jan 2;20(Suppl 1):1-2. PMID: 29323858.

3. Al-Gwaiz LA, Babay HH. The diagnostic value of absolute neutrophil count, band count and morphologic changes of neutrophils in predicting bacterial infections. Med Princ Pract. 2007;16(5):344-7. doi: 10.1159/000104806. PMID: 17709921.