From the Guidelines
Low neutrophils, or neutropenia, are typically diagnosed through a complete blood count (CBC) with differential, which is the first-line test due to its simplicity and comprehensive information about blood cell counts. This blood test measures the levels of different types of blood cells, including neutrophils. A neutrophil count below 1,500 cells per microliter of blood in adults is generally considered low 1. For more specific evaluation, additional tests may be ordered, including:
- Bone marrow aspiration and biopsy to examine neutrophil production
- Specialized blood tests to check for autoimmune conditions that might be destroying neutrophils
- Genetic testing if hereditary neutropenia is suspected, such as in the case of CD40 or CD40L deficiency, where flow cytometric methods on activated T cells or monocytes/B cells can be used to evaluate CD40L or CD40 expression, respectively 1
- If infection is present alongside neutropenia, blood cultures or other infection tests may be performed, and in cases of CD40 or CD40L deficiency, PCP prophylaxis is indicated due to the high risk of opportunistic infections 1. Neutropenia can result from decreased production in the bone marrow, increased destruction in the bloodstream, or excessive sequestration in the spleen, so identifying the underlying cause is crucial for proper treatment, which may include granulocyte colony-stimulating factor (G-CSF) therapy or hematopoietic stem cell transplantation (HSCT) in severe cases 1.
From the Research
Tests for Low Neutrophils
To diagnose and manage low neutrophils, also known as neutropenia, several tests can be conducted. These include:
- Complete blood cell counts (CBCs) with differentials to confirm neutropenia and examine the overall blood cell count 2, 3
- Bone marrow examination with cytogenetics to evaluate the bone marrow and identify any potential disorders or abnormalities 2, 3
- Neutrophil antibody testing, which may be useful in certain contexts, such as when clinical and bone marrow findings suggest an immune-mediated cause 2
- Genetic testing to diagnose congenital neutropenias, which is now possible due to the discovery of responsible genes 2
- Examination of a blood smear to evaluate the morphology of neutrophils and other blood cells 3
- Review of the patient's medical history, family history, and physical examination to identify potential causes of neutropenia 3
Diagnostic Evaluation
The diagnostic evaluation of neutropenia typically involves a stepwise approach, focusing first on reaching a provisional diagnosis and treatment plan, and then proceeding to further testing to confirm the diagnosis 4. This may include:
- Repeat CBCs with differentials to confirm the presence of neutropenia
- Bone marrow aspiration and/or biopsy to evaluate the bone marrow
- Cytogenetic testing to identify any chromosomal abnormalities
- Neutrophil antibody testing, if indicated
Monitoring and Management
Patients with severe chronic neutropenia require regular monitoring for potential complications, such as myelodysplastic syndromes (MDS) or acute myeloid leukemia (AML) 2, 4. Management of neutropenia may involve:
- Administration of granulocyte colony-stimulating factor (G-CSF) to increase neutrophil production 2, 4, 5
- Prophylactic antibiotics to prevent infections 6
- Aggressive treatment of bacterial or fungal infections 2, 4
- Hematopoietic stem cell transplantation, which is a curative therapy for congenital neutropenia with MDS/AML or cytogenetic abnormalities indicating impending conversion 2