This is NOT neutropenia and requires no intervention beyond reassurance and documentation of benign ethnic neutropenia.
An absolute neutrophil count (ANC) of 2.10 × 10⁹/L in a Black male patient is completely normal and does not represent neutropenia. This patient has benign ethnic neutropenia (BEN), a physiologic variant that affects 25-50% of individuals of African descent 1.
Understanding Benign Ethnic Neutropenia
The standard neutropenia threshold of 1.5 × 10⁹/L was established based on Caucasian populations and does not apply universally. Black individuals have physiologically lower baseline ANC values due to the Duffy-null phenotype [Fy(a-b-)], which is present in approximately 93% of Black individuals 2.
Population-Specific Reference Ranges
Recent evidence establishes that for Duffy-null individuals:
- The lower limit of normal ANC is 1.01 × 10⁹/L 3
- Median ANC values are significantly lower (1.45 vs. 4.45 × 10⁹/L in non-Duffy-null populations) 3
- This patient's ANC of 2.10 × 10⁹/L falls well within the normal range for Black individuals
Clinical Significance
Individuals with BEN have no increased susceptibility to infections and require no treatment or prophylaxis 1. The key determination is whether the bone marrow can produce adequate neutrophils when needed—not the absolute number in peripheral blood at baseline 1.
What This Patient Does NOT Need:
- Hematology referral
- Bone marrow biopsy
- G-CSF therapy
- Antimicrobial prophylaxis
- Serial monitoring beyond routine care
- Duffy phenotype testing (though this can confirm BEN if desired for documentation)
Documentation and Future Care
Document "benign ethnic neutropenia" in the medical record to prevent:
- Inappropriate hematology referrals (Black patients are disproportionately referred for asymptomatic neutropenia) 2
- Misclassification as pathologic neutropenia
- Unnecessary exclusion from clinical trials or chemotherapy protocols
- Repeated workups by future providers
When to Actually Worry
True pathologic neutropenia requiring evaluation occurs when 4, 5:
- ANC < 1.0 × 10⁹/L in Black patients (below the Duffy-null reference range)
- Patient develops fever (≥38.3°C single reading or ≥38.0°C sustained) 6
- Recurrent infections occur
- Other cytopenias are present
- Peripheral smear shows abnormalities (blasts, atypical cells, schistocytes)
Common Pitfall
The most critical error is applying Caucasian-derived reference ranges to all ethnic groups 7. This leads to overdiagnosis, unnecessary specialist referrals, and potential harm from inappropriate interventions. Studies show that among Black patients referred for neutropenia, hematologic disorders were rare (only 23% had clinically relevant findings), and nearly all who tested positive for Duffy-null phenotype had benign outcomes 2.
In this case: reassure the patient, document BEN in the chart, and proceed with routine care. No further action is needed.