Absolute Neutrophil Count (ANC)
Why Use
The calculation can be completed with a routine complete blood count and differential. It is a tool to provide a rapid risk stratification. No additional laboratory work is needed to complete the calculation.
When to Use
The ANC can be critical in assessing an immunocompromised patient’s risk for developing opportunistic infections. It is commonly used in the hospital setting, clinic, and emergency department. If a patient undergoing active myelosuppressive chemotherapy presents with a sustained fever (with or without localizing symptoms), there is a risk of progression to sepsis. Thus, it is imperative to calculate the ANC to assist in determining if empiric antibiotics should be initiated.
Formula
Pearls / Pitfalls
The ANC calculation is not a static measurement done only once upon hospital admission. Rather, it is often measured daily in critically ill patients to assess the bone marrow’s response after chemotherapy, for example. Recall that the ANC is dynamic – it is an absolute value and is expected to drop during the patient’s nadir after chemotherapy.
Management
Obtain a complete blood count with differential. ANC is calculated as 10 x WBC count in 1000s x (% PMNs + % bands). Classify neutropenia as mild, moderate, or severe as in Evidence . ANC values can also be interpreted by NCI risk categories: NCI Risk Category ANC 0 Within normal limits 1 ≥1,500 to <2,000 cells/mm 3 2 ≥1,000 to <1,500 cells/mm 3 3 ≥500 to <1,000 cells/mm 3 4 <500 cells/mm 3
Critical Actions
If the clinical scenario is suggestive of neutropenic fever, appropriate cultures and infectious disease workup should be instituted along with prompt initiation of empiric broad-spectrum antibiotics to cover mostly endogenous flora.
Advice
Neutropenic fever (without a source of infection found) is typically the result of direct toxic effects of chemotherapy on mucosal surfaces and the immune system in addition to the impact of the underlying malignancy. It is defined as a single oral temperature of 38.3ºC (101ºF) or a temperature of greater than 38.0ºC (100.4ºF) sustained for more than 1 hour in a patient with neutropenia. It is typically seen in those who have received anti-cancer therapies in the last 6 weeks. Filgrastim (Neupogen), a.k.a. G-CSF, can stimulate production of neutrophils, but is rarely indicated in the evaluation and treatment of neutropenic fever. Additional tools to risk stratify a neutropenic fever patient and predict complications include the Clinical Index of Stable Febrile Neutropenia (CISNE) and Multinational Association for Supportive Care in Cancer (MASCC) Score .
More Information
Neutropenia: ANC <1,500 cells/mm 3 Mild neutropenia: 1,000-1,500 cells/mm³ Moderate neutropenia: 500-999 cells/mm³ Severe neutropenia: <500 cells/mm³ Neutrophilia: ANC >7,700 cells/mm 3