Britannica
Sources used in this answer
How can a complete blood count help identify an infection?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
blood analysis
The physical and chemical properties of a sample of blood are examined during blood analysis. The examination of blood is important for the accurate diagnosis of disease.
A complete blood count (CBC) helps identify an infection by measuring the total number and types of white blood cells present in the blood. In a healthy individual, the immune system typically responds to an infection by increasing the production of these cells.12
A differential white blood cell count provides further diagnostic insight by identifying which specific types of white blood cells are abnormal:
- Viral infections: These typically affect the lymphocyte count.2
- Bacterial infections: These often lead to an increase in the percentage of band neutrophils.2
- Parasitic infections: These may cause an increase in eosinophils.2
While an increase in white blood cells (leukocytosis) is a common sign of infection, some infections or conditions can cause a decrease in white blood cell numbers, a state known as leukopenia. By analyzing these fluctuations, clinicians can gain essential information regarding the presence and potential nature of an infection.312