Incidence of Typical Neutrophil Count With Fy(a-b-) Status Among Hematology Referrals for Neutropenia at an Urban Safety-Net Hospital.

Background: Duffy-null associated neutrophil count (DANC) causes neutropenia without clinical sequelae. 25%-50% of people of African ancestry in the United States are thought to have Fy(a-b-) status and are often erroneously identified as having pathologically low neutrophil counts. Results: We performed a retrospective chart review of new neutropenia referrals to the Hematology Clinic at Boston Medical Center (BMC) to evaluate diagnostic patterns for Fy(a-b-) status. 103 new referrals for neutropenia were made from 1/2020 to 2/2022, of which 78 were included for further analysis. DANC was the etiology for low neutrophil count in 64.1%, 82% of whom were African American or Black or were born in an African or Caribbean country. 66% of these patients underwent confirmatory blood bank testing, and 97% of patients tested were confirmed to have Fy(a-b-) status. The average cost of a laboratory visit for patients with typical neutrophil count with Fy(a-b-) status was on average lower, but not negligible, than those without ($363.82 vs. $737.93; p < 0.005). These patients were also statistically less likely to have a follow-up appointment (p=0.039). Conclusions: Expanded use of serological Fy(a,b) antigen testing for patients with chronic, asymptomatic neutropenia could reduce the cost of care and referrals to the hematology clinic.