From the FDA Drug Label
The use of ZARXIO prior to confirmation of a correct diagnosis of SCN may impair diagnostic efforts and may thus impair or delay evaluation and treatment of an underlying condition‚ other than SCN‚ causing the neutropenia Monitor neutrophil counts after 4 days of ZARXIO‚ and discontinue ZARXIO if the white blood cell (WBC) count rises to greater than 100‚000/mm3.
The FDA drug label does not answer the question about the implications and treatment options for a low White Blood Cell (WBC) count in African Americans.
From the Research
A low white blood cell (WBC) count in African Americans often represents a benign ethnic variation called benign ethnic neutropenia rather than a pathological condition requiring treatment. For African Americans with WBC counts between 1,000-3,500 cells/μL without symptoms or infections, clinical monitoring is typically recommended rather than medical intervention 1. This condition affects approximately 25-50% of individuals of African descent and is characterized by lower neutrophil counts while maintaining normal immune function.
Key Considerations
- Benign ethnic neutropenia is driven by the Duffy null [Fy(a-b-)] phenotype, which is protective against malaria and seen in 80% to 100% of those of sub-Saharan African ancestry and <1% of those of European descent 1.
- The lower ANC levels in African Americans are common and harmless, with ANC reference ranges from countries in Africa emphasizing that ANC levels <1500 cells/μL are normal 1.
- If treatment is necessary due to severely low counts or recurrent infections, options include granulocyte colony-stimulating factors (G-CSF) like filgrastim (Neupogen) at 5-10 μg/kg/day subcutaneously until counts normalize.
- For patients undergoing chemotherapy with neutropenia, prophylactic antibiotics such as levofloxacin 500 mg daily may be prescribed.
Clinical Approach
- It's essential to establish each individual's baseline WBC count for future reference and to distinguish between benign ethnic neutropenia and pathological causes of low WBC counts such as medication effects, viral infections, or autoimmune disorders.
- Healthcare providers should avoid unnecessary antibiotic use or invasive procedures based solely on laboratory values without considering this normal variation, as African Americans with benign ethnic neutropenia generally maintain normal immune function despite lower absolute neutrophil counts 1.