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Management of Dengue Infection

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CBC

CBC Interpretation

Introduction to CBC

Definition and Components

A Complete Blood Count (CBC) is a laboratory test that evaluates the cellular components of blood. It provides crucial diagnostic and monitoring insights for various hematologic and systemic disorders. The major components include:

  1. Red Blood Cell (RBC) Parameters

    • RBC count
    • Hemoglobin (Hgb)
    • Hematocrit (Hct)
    • RBC indices: MCV, MCH, MCHC, RDW

  2. White Blood Cell (WBC) Parameters

    • Total WBC count
    • Differential WBC count (Neutrophils, Lymphocytes, Monocytes, Eosinophils, Basophils)

  3. Platelet Parameters

    • Platelet count
    • Mean Platelet Volume (MPV)
    • Platelet Distribution Width (PDW)

Indications and Clinical Uses

  • Anemia Evaluation
  • Infection and Inflammation (WBC abnormalities)
  • Bone Marrow Disorders (Leukemia, Myelodysplastic Syndromes)
  • Clotting and Bleeding Disorders (Thrombocytopenia, Thrombocytosis)
  • Systemic Conditions (Liver disease, Renal failure, Autoimmune disorders)

CBC/CBP report


Red Blood Cells (Erythrocytes) & Indices

1. RBC Count

  • Measures the number of circulating red blood cells (millions per microliter of blood).
  • Normal range:
    • Men: 4.7–6.1 million/µL
    • Women: 4.2–5.4 million/µL
    • Children: 4.1–5.5 million/µL
  • Elevated RBC count (Polycythemia): Dehydration, COPD, high altitude, polycythemia vera
  • Low RBC count (Anemia): Blood loss, hemolysis, bone marrow failure

2. Hemoglobin (Hgb) & Hematocrit (Hct)

Hemoglobin (Hgb)

  • The oxygen-carrying protein in RBCs
  • Normal range:
    • Men: 13.8–17.2 g/dL
    • Women: 12.1–15.1 g/dL

Hematocrit (Hct) Formula:

Hct(%)=RBC×MCV10Hct (\%) = \frac{RBC \times MCV}{10}
  • Measures the proportion of blood volume occupied by RBCs
  • Normal range:
    • Men: 42–52%
    • Women: 37–47%

3. Red Cell Indices

Mean Corpuscular Volume (MCV) – Size of RBCs

MCV=Hct(%)RBC×10MCV = \frac{Hct (\%)}{RBC} \times 10
  • Normal: 80–100 fL
  • Microcytic Anemia (MCV < 80 fL) → Iron deficiency, thalassemia
  • Macrocytic Anemia (MCV > 100 fL) → B12/Folate deficiency, alcoholism

Mean Corpuscular Hemoglobin (MCH)

MCH=HgbRBC×10MCH = \frac{Hgb}{RBC} \times 10
  • Normal: 27–31 pg/cell
  • Low: Hypochromic anemias
  • High: Macrocytosis

Mean Corpuscular Hemoglobin Concentration (MCHC)

MCHC=HgbHct×100MCHC = \frac{Hgb}{Hct} \times 100
  • Normal: 32–36 g/dL
  • Low: Hypochromic anemias
  • High: Spherocytosis

Red Cell Distribution Width (RDW) – RBC Size Variation

RDW(%)=StandardDeviationofMCVMeanMCV×100RDW (\%) = \frac{Standard Deviation of MCV}{Mean MCV} \times 100
  • Normal: 11.5–14.5%
  • Increased RDW: Iron deficiency, mixed anemia types

4. Reticulocyte Count (Bone Marrow Activity Indicator)

  • Formula:
CorrectedReticulocyteCount=Reticulocyte%×Hct45Corrected Reticulocyte Count = Reticulocyte \% \times \frac{Hct}{45}
  • Normal: 0.5–2.5%
  • High: Hemolysis, blood loss
  • Low: Bone marrow suppression


White Blood Cells & Differential Count

1. Total WBC Count

  • Normal: 4,000–11,000/µL
  • Leukocytosis (>11,000/µL): Infection, leukemia, stress
  • Leukopenia (<4,000/µL): Bone marrow suppression, viral infections

2. Differential WBC Count

  • Neutrophils (55–70%) – Bacterial infections
  • Lymphocytes (20–40%) – Viral infections, chronic conditions
  • Monocytes (2–8%) – Chronic infections, TB
  • Eosinophils (1–4%) – Allergies, parasitic infections
  • Basophils (<1%) – Allergies, chronic inflammation

3. Neutrophil-to-Lymphocyte Ratio (NLR) in Disease Prognosis

NLR=AbsoluteNeutrophilCountAbsoluteLymphocyteCountNLR = \frac{Absolute Neutrophil Count}{Absolute Lymphocyte Count}
  • Higher NLR: Predicts worse prognosis in infections, cancer


Platelet Count & Function

1. Platelet Count

  • Normal: 150,000–450,000/µL
  • Thrombocytosis (>450,000/µL): Inflammation, malignancy
  • Thrombocytopenia (<150,000/µL): ITP, DIC, leukemia

2. Platelet Indices

  • Mean Platelet Volume (MPV): 7.5–11.5 fL
  • Platelet Distribution Width (PDW): Increased in platelet disorders


Peripheral Blood Smear Correlation

  • RBC Morphology: Target cells (Thalassemia), Schistocytes (DIC)
  • WBC Abnormalities: Blast cells (Leukemia), Toxic granulation (Infection)
  • Platelet Morphology: Giant platelets (ITP), Clumping


Interpretation in Specific Clinical Scenarios

1. Infection & Inflammation Patterns

  • High neutrophils (Bacterial), High lymphocytes (Viral)

2. Anemia Workup

  • Microcytic: Iron deficiency
  • Normocytic: Chronic disease
  • Macrocytic: B12/Folate deficiency

3. Bone Marrow Disorders

  • Leukemia, Myelodysplasia

4. Platelet Disorders

  • ITP, TTP, DIC


Conclusion & Further Workup

  • Additional Tests: Bone marrow biopsy, Iron studies, Vitamin B12/Folate
  • Role in Disease Monitoring: Chronic anemia, leukemia


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