Complete Blood Count (CBC) Overview

Complete Blood Count (CBC)

• A CBC blood test is used to monitor or diagnose health conditions, including blood cancers, anemia, and infections.
• CBC can also follow the progress of medical conditions and diagnose diseases that affect WBC and platelet count.
• CBC uses automated instruments like Coulter to measure blood components.

Interpreting CBC Results

• Hemoglobin (Hb) concentration is the amount of oxygen-carrying protein in red blood cells.
  • Normal values: 11.5-15.5 g/dl for adults.
• Hematocrit (Hct) or packed cell volume (PCV) is the percentage of red blood cells in total blood volume.
  • Normal values: 36-45% for adults.
• Red Blood Cell (RBC) count is the number of red blood cells per unit of blood.
  • Normal values: 4.0-5.2 million/cmm for adults.
• Mean Corpuscular Volume (MCV) is the average volume of a red blood cell.
  • Normal values: 80-100 fl (femtoliters). Used to categorize red blood cells by size.
• Mean Corpuscular Hemoglobin (MCH) is the average weight of hemoglobin content in a red blood cell.
  • Normal values: 27-33 pg (picograms).
• Mean Corpuscular Hemoglobin Concentration (MCHC) is the average concentration of hemoglobin in 100 ml of red blood cells.
  • Normal values: 31-37 g/dl. Categorizes red blood cells according to their hemoglobin concentration.
• Red Cell Distribution Width (RDW) is a measure of the variation in red blood cell size.
  • Normal values: 11.5-15%. A high RDW indicates more variation in red blood cell size.
• Platelet count is the number of platelets per unit of blood.
  • Normal values: 150-450 thousands/cmm.
• Total Leucocytic Count (TLC) is the total number of white blood cells in a sample.
  • Normal values: 4-11 thousands/cmm.
• Differential Leucocytic Count (DLC) is the percentage of each type of white blood cell in a sample.

Polycythemia (Increased RBC Count)

• Is an increase in red blood cells.
• Can be caused by factors such as:
  • High altitude living
  • Certain cancers
  • Dehydration

Anemia (Decreased RBC Count)

• Is a decrease in red blood cells.
• Can be caused by factors such as:
  • Iron deficiency
  • Vitamin B12 deficiency
  • Chronic diseases

Hemoglobin Concentration

• Normal Value:

  • Adult Male: 16 ± 2 gm /dl
  • Adult Female: 14 ± 2 gm /dl

• Increased Hb concentration (Polycythemia)

• Decreased Hb concentration (Anemia)

Types of Hemoglobin

• Hemoglobin A
• Hemoglobin F
• Hemoglobin S (Sickle cell anemia)

Cyanmethemoglobin Method

• It is the internationally recommended method to determine hemoglobin concentration in blood.
• Uses potassium ferricyanide and potassium cyanide.
• The color intensity of the cyanmethemoglobin complex is directly proportional to the hemoglobin concentration.
• The absorbance of the colored complex is measured at 540 nm.

Hematocrit Value (Hct) or Packed Cell Volume (PCV)

• It is the percentage of red blood cells in total blood volume.
• Normal values:
  • Adult males: 45%
  • Adult Females: 42%
  • Infant at birth: 60%
  • Children 6-12 y: 40%

Measuring Hct

• Can be measured by:
  • Coulter
  • Microhematocrit method
  • Wintrobe's method

Hct Uses

• Determination of blood volume
• Helps to determine the type of anemia

Physiological and Pathological Factors Affecting Hct

• Dehydration
• Anemia
• Polycythemia

Red Cell Indices

• Measurements that describe the size and hemoglobin content of red blood cells.
• Help to classify anemias.

Mean Corpuscular Volume (MCV)

• Measures the average volume of a red blood cell.
• Calculation: MCV = (Hct x 10 / RBCs count in millions/mm³)
• Normal value: 80-95 fl (femtoliters).

Morphologic Classification of Anemia Based on MCV

• Low MCV: Microcytic- Iron deficiency anemia
• Normal MCV: Normocytic- Chronic disease, Renal failure
• High MCV: Macrocytic- Vitamin B12 and folic acid deficiency anemia

Mean Corpuscular Hemoglobin (MCH)

• Average weight of hemoglobin content in a red cell.
• Calculation: MCH = (Hb content (g/100 ml) x 10 / RBCs count in millions/mm³)
• Normal value: 27-31 pg (picograms).

Mean Corpuscular Hemoglobin Concentration (MCHC)

• Measures the average concentration of hemoglobin in 100 ml of red blood cells.
• Calculation: MCHC = (Hb content (g/100 ml) x 100 / Hct)
• Normal value: 30-35 g/100 ml of RBCs.

Total Leukocytic Count (TLC)

• Normal value: 4,000–11,000 / mm³.
• Leukocytosis: Increased WBCs count > 11,000 / mm³ in adult.
• Leukopenia: Decreased WBCs count < 4,000 / mm³ in adult.

Differential Leukocytic Count (DLC)

• Percentages of each type of white blood cell in a sample.
  • Neutrophils (60-70%)
  • Eosinophils (1-4%)
  • Basophils (0.25-0.5%)
  • Lymphocytes (25-33%)
  • Monocytes (2-6%)

Platelet Count

• Normal value: 150-450 x10³/mm³ of blood
• Thrombocytosis: High platelet count
• Thrombocytopenia: Low platelet count

Causes of Thrombocytosis

• Reactive thrombocytosis: blood loss, cancer, infection.
• Abnormal platelet production in bone marrow.

Causes of Thrombocytopenia

• Bone marrow depression
• Autoimmune disease
• Other reasons