Which lab value defines neutropenia?

• A. ANC < 1.5 x10^9
• B. ANC < 2.0 x10^9
• C. ANC < 0.5 x10^9
• D. ANC < 3.0 x10^9

Answer: (A)

Neutropenia is defined by a low absolute neutrophil count, which reflects the body's frontline defense against bacterial infections. The standard cutoff used in practice is an ANC below 1.5 x 10^9/L. This threshold is chosen because when the ANC falls under 1.5, infection risk rises and clinicians begin to monitor more closely or implement preventive measures; it also helps guide decisions about antifungal or antibiotic prophylaxis and adjustments to therapy. The ANC is calculated from the white blood cell count and the differential: ANC = WBC x (neutrophils plus bands as a percentage). For reference, severe neutropenia is typically defined as ANC below 0.5 x 10^9/L, which carries a much higher infection risk. Values around 2.0 or 3.0 x 10^9/L are not neutropenic by the standard definition, and 2.0 x 10^9/L would generally be considered within or near the lower end of the normal range rather than neutropenia.