Joel Bervell, MD on Instagram: "The Duffy-null phenotype is a genetic variant found in two-thirds of people who self-identify as Black in the United States. Individuals who have it have low neutrophil (white blood cell) levels without an increased risk of infection. But because the neutrophil reference ranges were created based on people of European descent, not taking into account the Duffy-null phenotype has played a direct contribution to unnecessary procedures like bone marrow biopsies, excl