27/06/2026
Complete Blood Count (CBC)
Definition
The Complete Blood Count (CBC) is a routine hematological test used to evaluate the cellular components of blood. It measures red blood cells (RBCs), white blood cells (WBCs), hemoglobin, hematocrit, platelet count, and related indices to assess overall health and detect a wide range of disorders.
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Principle
CBC is based on the quantitative and qualitative analysis of blood cells using an automated hematology analyzer. The analyzer works on principles such as electrical impedance, flow cytometry, and light scattering to count and differentiate blood cells accurately.
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Objectives
1. To evaluate overall health status.
2. To detect anemia and infections.
3. To diagnose hematological disorders.
4. To monitor disease progression and response to treatment.
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Components of CBC
1. Red Blood Cell Parameters
RBC count
Hemoglobin (Hb)
Hematocrit (Hct)
Red cell indices: MCV, MCH, MCHC, RDW
2. White Blood Cell Parameters
Total WBC count
Differential count: Neutrophils, Lymphocytes, Monocytes, Eosinophils, Basophils
3. Platelet Parameters
Platelet count
Mean Platelet Volume (MPV)
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Materials Required
EDTA anticoagulated blood sample
Sterile syringe/needle
Tourniquet
Alcohol swab
Cotton/gauze
Hematology analyzer
Gloves (PPE)
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Procedure
1. Explain the procedure to the patient and obtain consent.
2. Collect venous blood using aseptic technique.
3. Transfer blood into an EDTA tube.
4. Mix gently by inverting the tube 8–10 times.
5. Load the sample into the hematology analyzer.
6. Analyzer measures and displays results.
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Normal Reference Values (Adults – Approximate)
Hemoglobin:
Male: 13.5–17.5 g/dL
Female: 12.0–15.5 g/dL
Total WBC count: 4,000–11,000 /µL
Platelet count: 150,000–450,000 /µL
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Interpretation
Low Hb/RBC → Anemia, blood loss, nutritional deficiency
High WBC → Infection, inflammation, leukemia
Low WBC → Viral infection, bone marrow disorder
Low Platelets → Bleeding disorders, dengue, ITP
High Platelets → Inflammation, iron deficiency
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Clinical Significance
Helps diagnose anemia, infections, and inflammatory conditions.
Essential for routine health check-ups and pre-surgical evaluation.
Useful in monitoring chemotherapy and chronic diseases.
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Advantages
1. Simple and quick test.
2. Widely available and cost-effective.
3. Provides comprehensive information about blood health.
4. Useful for early disease detection.
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Limitations
1. Does not give a definitive diagnosis alone.
2. Results may be affected by dehydration, drugs, or pregnancy.
3. Abnormal findings may require further confirmatory tests.
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Conclusion
The Complete Blood Count (CBC) is a fundamental laboratory investigation that provides vital information about blood cells and overall health. It plays a crucial role in diagnosis, screening, and monitoring of many medical conditions.
