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Absolute Neutrophil Count

The absolute neutrophil count (ANC) is equal to the product of the white blood cell count (WBC) and the fraction of polymorphonuclear cells (PMNs) and band forms counted in the WBC differential analysis. The formula is:

ANC = WBC (cells/uL) x percent (PMNs+bands)/100

ANC is often measured daily in critically ill patients to assess the bone marrow’s response after chemo­therapy. It is ordered for both inpatients and outpatients. ANC can be used to classify neutropenia as mild, moderate or severe:

  • Mild neutropenia: 1000-1500 cells/uL (1.0-1.5 x 103/uL)
  • Moderate neutropenia: 500-999 cells/uL (0.5 - 0.99 x 103/uL)
  • Severe neutropenia: < 500 cells/uL (<0.5 x 103/uL) 

ANC is frequently used to assess neutropenic fever in chemotherapy patients. ANC should be used in neutropenic patients with a fever of at least 38ºC (100.4°F) to assess the risk of progression to sepsis. The risk of infection begins to increase at an ANC below 1000 cells/uL and is inversely related to the ANC.  The source of microbial invasion of the blood in these patients is often chemotherapy-induced mucositis and breaks in the gastrointestinal lining. In general, patients with an ANC of <500/uL and marrow aplasia are treated with parenteral antibiotics. Patients with indwelling catheters or other foreign bodies are more likely to become infected with coagulase-negative staphylococci.

According to the Infectious Disease Society of America (IDSA) guidelines, ANC should not be used in patients with acute leukemia who are undergoing induction chemother­apy or allogeneic hematopoietic stem cell transplant conditioning.

Many laboratories consider an ANC of <500 cells/uL to be a critical value. This decision is based upon the following evidence. Al-Gwaiz et al (2007) tested the ability of ANC to predict bacterial infections. They examined 105 peripheral blood smears and determined ANC, as well as the sensitivity of predicting bacterial infec­tions. ANC and toxic granulations were more sensitive than band count in predicting bacterial infections. Rivera et al (2003) performed a cross-validation study of Silber et al’s 1998 findings to test if the first-cycle nadir ANC pre­dicted the risk of febrile neutropenia. An ANC of  ≤ 0.5 x 103/uL was associated with a relative odds ratio of 4.8. 

References

  1. Al-Gwaiz LA, Babay HH. The diagnostic value of absolute neutrophil count, band count and morphologic changes of neutrophils in predicting bacterial infections. Med Princ Pract. 2007;16(5):344-347. 
  2. Carmona-Bayonas A, Jiménez-Fonseca P, Virizuela Echa­buru J, et al. Prediction of serious complications in patients with seemingly stable febrile neutropenia: validation of the Clinical Index of Stable Febrile Neutropenia in a prospective cohort of patients from the FINITE study. J Clin Oncol. 2015 Feb 10;33(5):465-471. 
  3. Silber JH, Fridman M, Dipaola RS, et al. First-cycle blood counts and subsequent neutropenia, dose reduction, or delay in early-stage breast cancer therapy. J Clin Oncol. 1998;16(7):2392-2400. 
  4. Rivera E, Haim Erder M, Fridman M, et al. First-cycle abso­lute neutrophil count can be used to improve chemothera­py-dose delivery and reduce the risk of febrile neutropenia in patients receiving adjuvant therapy: a validation study. Breast Cancer Res. 2003;5(5):R114-R120. 
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