How to Calculate Absolute Neutrophil Count (ANC) from a CBC
The ANC is calculated by multiplying the total white blood cell (WBC) count by the percentage of neutrophils (segmented neutrophils plus bands), then dividing by 100. 1
The Calculation Formula
ANC = WBC × (% Segmented Neutrophils + % Bands) ÷ 100
- The calculation requires two components from the CBC: the total WBC count and the differential percentage showing segmented neutrophils and bands 2
- When the WBC is reported in cells/µL or ×10⁹/L, ensure you maintain consistent units throughout the calculation 1
- The resulting ANC will be in the same units as your WBC count (typically cells/µL or ×10⁹/L) 3
Step-by-Step Calculation Process
Step 1: Obtain the total WBC count from the CBC (e.g., 8,000 cells/µL or 8.0 × 10⁹/L) 2
Step 2: Identify the percentage of segmented neutrophils from the differential (e.g., 50%) 1
Step 3: Identify the percentage of bands (immature neutrophils) from the differential (e.g., 5%) 1
Step 4: Add the segmented neutrophils and bands together (50% + 5% = 55%) 2
Step 5: Multiply the WBC by this combined percentage and divide by 100:
- ANC = 8,000 × 55 ÷ 100 = 4,400 cells/µL 1
Clinical Interpretation of Results
Neutropenia severity classification based on calculated ANC: 1
- Normal: ANC ≥1.5 × 10⁹/L (1,500 cells/µL)
- Mild neutropenia: ANC 1.0-1.5 × 10⁹/L (1,000-1,500 cells/µL) 1
- Moderate neutropenia: ANC 0.5-1.0 × 10⁹/L (500-1,000 cells/µL) 1
- Severe neutropenia: ANC <0.5 × 10⁹/L (<500 cells/µL) 1
Important Technical Considerations
Automated vs. manual differential counts:
- Modern 5-part differential hematology analyzers (such as Sysmex XE-2100 or Advia 2120i) provide accurate and precise ANC values even at very low levels (>0.1 × 10⁹/L), with excellent correlation to flow cytometric reference methods 3
- Automated ANC determination is acceptable for clinical decision-making and shortens turnaround time in outpatient settings 4
- Manual 100-cell differentials may show variation of -55% to +33% compared to automated counts, with a standard deviation of 14% 4
- When ANC is critically low (<0.5 × 10⁹/L), consider confirming with manual differential or repeat testing if clinical decisions depend on precise values 3
Common Pitfalls to Avoid
Do not include other white blood cell types in the neutrophil calculation - only segmented neutrophils and bands should be counted, not lymphocytes, monocytes, eosinophils, or basophils 2
Ensure the CBC and differential are from the same blood draw - when calculating absolute values for clinical decisions (such as chemotherapy eligibility), the WBC count and differential must be from simultaneously drawn blood 2
Watch for spuriously elevated or lowered automated counts - certain conditions can affect automated analyzer accuracy, particularly in patients with circulating blasts, nucleated red blood cells, or other abnormal cells 4