Kylee L. Martens

Background Asymptomatic neutropenia is a common hematology referral, though standardized reference ranges and published clinical outcomes are lacking. Methods In our retrospective analysis, we evaluated demographics, laboratory, and clinical outcomes of adult patients referred to an academic hematology practice for evaluation of neutropenia from 2010 to 2018. Primary and secondary outcomes included incidence of hematologic disorders and rates of Duffy‐null positivity by race, respectively. In a separate analysis, we reviewed absolute neutrophil count (ANC) reference ranges from publicly available Association of American Medical Colleges Medical School Member laboratory directories to assess institutional variations. Results In total, 163 patients were included, with disproportionate number of Black patients referred compared to local demographics. Twenty‐three percent of patients ( n = 38) were found to have a clinically relevant hematologic outcome (mean ANC of 0.59 × 10 9 /L), and only six were identified with ANC ≥1.0 × 10 9 /L. Incidence of hematologic outcomes was lowest among Black patients ( p = .05), and nearly all Blacks who underwent Duffy‐null phenotype testing were positive (93%), compared to 50% of Whites ( p = .04). In separate review of laboratory directories, we confirmed wide variation in ANC lower limit of normal (0.91–2.40 × 10 9 /L). Conclusion Hematologic disorders were rare in patients with mild neutropenia and among Blacks, highlighting the need to standardize hematological ranges representative of non‐White communities.