Incidental neutropenia: An emergency medicine focused approach

Neutropenia is defined as an absolute neutrophil count (ANC) < 1500 cells/microL and may be discovered incidentally in an asymptomatic, afebrile patient.

This narrative review provides an approach to the afebrile emergency department patient with incidental neutropenia.

Neutropenia is an ANC < 1500 cells/microL, with mild neutropenia defined as an ANC ≥ 1000 to <1500 cells/microL, moderate ≥500 to <1000 cells/microL, severe <500 cells/microL, and agranulocytosis <200 cells/microL. Incidental or isolated neutropenia is an ANC < 1500 cells/microL discovered on laboratory testing unrelated to the patient's chief complaint (e.g., chest pain, abdominal pain, shortness of breath, etc.) and not associated with fever or infectious signs and symptoms. There are a variety of etiologies, with inherited forms, dose-dependent drug-induced neutropenia, and infections the most common causes. Testing includes complete blood count with differential and peripheral smear. Management is based on the patient's hemodynamic status, presence of fever, severity of neutropenia, and the peripheral smear. Patients who are critically ill, febrile, have severe neutropenia, or have a concerning peripheral smear (schistocytes, atypical lymphocytes) should undergo hematology consultation. Those with critical illness or fever with neutropenia should receive broad-spectrum antibiotics. Patients who are afebrile, hemodynamically stable, and non-toxic appearing with mild or moderate neutropenia can likely be discharged for repeat testing in one to two weeks.

Understanding the approach to incidental neutropenia can improve patient care. Critically ill or febrile patients should be admitted, but select patients may be discharged.