Absolute Neutrophil Count by Duffy Status Among Healthy Black and African American Adults.

Many people of African ancestry have lower absolute neutrophil counts (ANC) without increased risk for infection. This is associated with the Duffy null phenotype (non-expression of the Duffy antigen on red blood cells), which is commonly found in those of African descent. Currently, there are no studies that compare the ANC of individuals with Duffy null phenotype to those with Duffy non-null phenotypes within a self-identified Black population. This study aimed to assess the impact of Duffy status on ANC in a healthy population of self-identified Black individuals by adding on a complete blood count with differential as well as a Duffy testing to individuals at a single primary care center. This study found that 66.7% (80/120) of Black individuals have the Duffy null phenotype, and there is a significant difference in ANC between Duffy null and Duffy non-null individuals (Median: 2,820 cells/uL vs 5,005 cells/uL; p<0.001). Additionally, 23.8% (19/80) of Duffy null individuals had an ANC<2,000 cells/uL compared to no Duffy non-null individuals. The Duffy null phenotype is clinically insignificant, but inappropriate reference ranges can propagate systemic racism. Thus, we advocate for development of Duffy null specific ANC reference ranges as well as replacing the term "benign ethnic neutropenia" with Duffy-null associated neutrophil count (DANC).