From the Guidelines
Neutrophils play a crucial role in the human body's defense against infections, and their levels should be monitored and managed to prevent infections, particularly in individuals with depressed absolute neutrophil counts due to HIV disease or drug therapy, as evidenced by the 2013 study 1.
Neutrophil Function and Importance
Neutrophils are the most abundant type of white blood cells in the human body, making up about 60-70% of all circulating white blood cells. They serve as the first line of defense against infections, particularly bacterial and fungal infections. When an infection occurs, neutrophils rapidly migrate to the site of infection through a process called chemotaxis, where they engulf and destroy pathogens through phagocytosis and by releasing antimicrobial substances.
Neutrophil Count and Infections
A normal neutrophil count ranges from 2,500 to 7,500 cells per microliter of blood. Elevated neutrophil counts (neutrophilia) often indicate an active infection, inflammation, or stress, while decreased counts (neutropenia) can result from certain medications, autoimmune disorders, or bone marrow problems, potentially increasing the risk of infections. According to the 1999 USPHS/IDSA guidelines 1, an absolute neutrophil count that is depressed due to HIV disease or drug therapy is associated with an increased risk for bacterial infections, including pneumonia.
Management of Neutropenia
To reduce the risk of bacterial infections in individuals with neutropenia, providers may consider taking steps to reverse neutropenia, either by stopping myelosuppressive drugs or by administering granulocyte-colony-stimulating factor (G-CSF), as recommended by the 2013 study 1. The study also notes that patients with severe chronic neutropenia, such as those with congenital or cyclic neutropenia, may require G-CSF therapy to normalize their neutrophil counts and prevent infections. The optimal dose of G-CSF varies depending on the type and severity of neutropenia, but generally ranges from 1-10 mcg/kg/d, with doses adjusted to maintain a blood neutrophil level in the normal or low-normal range 1.
From the Research
Definition and Diagnosis of Neutropenia
- Neutropenia is defined as an absolute neutrophil count (ANC) less than 1.5 × 10(9)/L 2
- Severe neutropenia is defined as an ANC less than 0.5 × 10(9)/L, which is a well-known risk factor for susceptibility to bacterial infections 2
- Diagnosis of neutropenia involves laboratory evaluation, including repeat complete blood cell counts (CBCs) with differentials and bone marrow examination with cytogenetics 3
Treatment of Neutropenia
- Granulocyte colony-stimulating factor (G-CSF) is a common treatment for severe chronic neutropenia, which can increase the ANC and reduce the risk of infections 2, 4, 5
- G-CSF treatment has been shown to be effective in increasing the ANC in patients with congenital, cyclic, and idiopathic neutropenia 4, 5
- Patients with severe chronic neutropenia may require long-term G-CSF treatment, which can be associated with adverse events such as thrombocytopenia, osteoporosis, and vasculitis 4
Risks and Complications of Neutropenia
- Patients with congenital neutropenia are at risk of developing myelodysplastic syndromes (MDS) or acute myeloid leukemia (AML), particularly those who respond poorly to G-CSF treatment 4, 5, 3
- Cyclic, idiopathic, and autoimmune neutropenia are not associated with an increased risk of MDS or AML 5, 3
- Hematopoietic stem cell transplantation is a curative therapy for congenital neutropenia with MDS/AML or with cytogenetic abnormalities indicating impending conversion 3