The Duffy antigen: A narrative review of testing, epidemiology, neutrophil counts and clinical consequences.

The null variant of the Duffy antigen is a non-pathological mutation that is partially protective against Plasmodium vivax and results in a lower absolute neutrophil count (ANC) in peripheral blood without increasing the risk of infection. Healthcare practices, clinical trials eligibility and medication dosing are often influenced by the definition of neutropenia. In many regions, however, neutropenia has been defined by the ANC distribution of Duffy-positive individuals, which may be unsuitable for decision-making in Duffy null individuals. This review describes the association between Duffy status, Plasmodium vivax exposure, racial or ethnic groupings and ANC. We outline biological and iatrogenic associations between Duffy antigen status and health outcomes and recommend changes to healthcare practices required to ensure equity for Duffy null individuals.