White Blood Cell Differential Testing
Direct Answer
The blood test that checks for specific white blood cell breakdown is the Complete Blood Count (CBC) with Differential, which identifies and quantifies the different types of white blood cells including neutrophils, lymphocytes, monocytes, eosinophils, and basophils. 1, 2
How the Test Works
The white blood cell differential is performed through a multi-step process:
- Automated WBC count and differential counting 10,000 to 30,000 cells provides the initial breakdown of white blood cell types 1
- Manual differential of at least 400 cells can be performed if the automated specimen is rejected or "flagged" by the instrument 1
- The differential provides both percentages and absolute counts of each white blood cell type 2
Advanced White Blood Cell Analysis
For more detailed white blood cell subset analysis, flow cytometric immunophenotyping provides specific identification of lymphocyte subpopulations:
- This technique uses fluorochrome-labeled monoclonal antibodies to detect specific antigenic determinants on white blood cell surfaces 1
- Flow cytometry categorizes individual cells according to size, granularity, fluorochrome type, and fluorochrome intensity 1
- Size and granularity distinguish the major WBC types: granulocytes, monocytes, and lymphocytes 1
- Different fluorochromes distinguish subpopulations within each WBC type 1
Clinical Applications
The white blood cell differential is essential for:
- Diagnosing infections, certain cancers, allergies, and immunodeficiencies 3
- Monitoring side effects of certain drugs that cause blood dyscrasias 3
- Assessing immune system status in various clinical conditions 4
- Baseline monitoring before initiating certain medications such as biologics 2
Quality Standards for Accurate Results
For reliable differential counts:
- Automated differentials should achieve at least 90% lymphocyte purity within the lymphocyte gate (minimally 85%) 2
- Results should be evaluated against established reference ranges that may vary by laboratory, age, and sex 2
- Absolute lymphocyte subset values are calculated by multiplying the lymphocyte subset percentage by the absolute number of lymphocytes from the WBC count 2