Absolute Neutrophil Count (ANC)

Absolute neutrophil count = 10 x WBC count x (% PMNs + % bands)

Note: assumes WBC count in 1,000s (i.e., x 10³ cells/µL, also equivalent to x 10³ cells/mm³).

Example, normal patient:

• CBC shows WBC 9.2 (units are x 10³ cells/µL), 33% neutrophils, and 1% bands.
• ANC = 10 x 9.2 x (33 + 1)
• ANC = 10 x 9.2 x 34
• ANC = 3,128 cells/µL → normal, no neutropenia

Example, neutropenic patient:

• CBC shows WBC 1.0 (units are x 10³ cells/µL), 11% neutrophils, and 5% bands.
• ANC = 10 x 1 x (11 + 5)
• ANC = 160 cells/µL → severe neutropenia

A study testing the application of ANC was done to predict bacterial infections. They examined 105 peripheral blood smears and along with the ANC, determined the sensitivity of predicting bacterial infections. ANC and toxic granulations are more sensitive than the band count in predicting bacterial infections. A validation study tested if the first-cycle nadir ANC predicted the risk of febrile neutropenia. This was a cross-validation study. An ANC of less than or equal to 0.5 x 10⁹/liter was associated with a relative odds ratio of 4.8. The goal of this study was to provide a foundation for which dose adjustments in chemotherapy can be made to provide maximal anti-neoplastic therapy while minimizing side effects.

Neutropenia: ANC <1,500 cells/mm³

• Mild neutropenia: 1,000-1,500 cells/mm³
• Moderate neutropenia: 500-999 cells/mm³
• Severe neutropenia: <500 cells/mm³

Neutrophilia: ANC >7,700 cells/mm³

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.

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.

• 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.

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.

• 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:

• 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.