From the Guidelines
Febrile neutropenia is characterized by a neutrophil count below 500 cells/mm³ (or expected to fall below 0.5 x 10^9/l), accompanied by a fever of 38.5°C or higher, or two consecutive readings of 38.0°C for 2 h. This definition is based on the most recent and highest quality study available, which provides clear guidelines for the management of febrile neutropenia 1.
Key Characteristics
- Neutrophil count: less than 0.5 x 10^9/l, or expected to fall below this level
- Fever: oral temperature greater than 38.5°C, or two consecutive readings of greater than 38.0°C for 2 hours
- C-Reactive Protein (CRP) levels are not explicitly defined in the guidelines, but are typically elevated in response to infection
Clinical Significance
The combination of neutropenia and fever is clinically significant because it indicates a compromised immune system, making patients vulnerable to severe infections. Even minor infections can rapidly progress to life-threatening sepsis in these patients, which is why febrile neutropenia is considered a medical emergency requiring immediate antibiotic therapy. The condition is most commonly seen in patients undergoing chemotherapy for cancer, particularly hematologic malignancies, but can occur in any situation where neutrophil production is impaired or neutrophil destruction is accelerated. More recent guidelines also provide definitions for fever and neutropenia, including a single oral temperature of ≥ 38.3°C (101°F) or a temperature ≥ 38.0°C (100.4°F) sustained over a 1-hour period, and an absolute neutrophil count < 1,000/mL (equivalent to < 1.0 x 10^9/L) for neutropenia 1. However, the most recent and highest quality study available is used to inform the definition of febrile neutropenia.
From the Research
Characterization of Febrile Neutropenia
- Febrile neutropenia is defined by an absolute neutrophil count (ANC) less than or equal to 500 cells per microliter with a concurrent single oral body temperature of more than or equal to 38.3° C (orally) or more than 38.0° C maintained over one hour 2, 3.
- The characterization of febrile neutropenia also involves the presence of fever, which is a critical component of the diagnosis 3, 4.
- C-Reactive Protein (CRP) levels are not explicitly mentioned in the provided studies as a characteristic of febrile neutropenia, but the focus is on neutrophil count and fever 2, 3, 5, 6, 4.
Neutrophil Count
- An absolute neutrophil count (ANC) of less than or equal to 500 cells per microliter is a key characteristic of febrile neutropenia 2, 3, 5, 6, 4.
- Patients with an ANC less than 100/mm³ have been shown to have a lower treatment success rate 3.
Fever
- Fever is defined as an oral body temperature of more than or equal to 38.3° C (orally) or more than 38.0° C maintained over one hour 2, 3.
- The presence of fever is a critical component of the diagnosis of febrile neutropenia 3, 4.