What labs are included in a Complete Blood Count (CBC)?

Components of a Complete Blood Count (CBC)

A Complete Blood Count (CBC) includes measurements of red blood cells, white blood cells, platelets, and related parameters that provide critical information about a patient's blood composition and potential health conditions. 1

Core CBC Components

• Red Blood Cell (RBC) Count: Quantifies the number of red blood cells, with abnormalities potentially indicating bone marrow disorders, bleeding, or hemolysis 1, 2

• Hemoglobin (Hb): Measures the oxygen-carrying protein in red blood cells; low values indicate anemia while high values suggest polycythemia 1, 3

• Hematocrit (Hct): Represents the percentage of blood volume occupied by red blood cells, providing information about oxygen-carrying capacity 1, 2

• Red Blood Cell Indices:

  • Mean Corpuscular Volume (MCV): Average size of red blood cells; helps classify anemias as microcytic, normocytic, or macrocytic 1, 4
  • Mean Corpuscular Hemoglobin (MCH): Average amount of hemoglobin per red blood cell 2
  • Mean Corpuscular Hemoglobin Concentration (MCHC): Average concentration of hemoglobin in a given volume of red blood cells 2
  • Red Cell Distribution Width (RDW): Measures variation in red blood cell size; increased in certain anemias 3, 2

• White Blood Cell (WBC) Count: Total number of white blood cells, which are critical for immune function 1, 3

• WBC Differential: Breakdown of white blood cell types, including:

  • Neutrophils: First responders to bacterial infections 3
  • Lymphocytes: Important for immune response 3
  • Monocytes: Involved in inflammatory response 2
  • Eosinophils: Elevated in allergic reactions and parasitic infections 5
  • Basophils: Involved in inflammatory reactions 2

• Platelet Count: Measures cells involved in blood clotting; low counts increase bleeding risk while high counts may indicate inflammation or myeloproliferative disorders 1, 3

Additional Parameters Sometimes Included

• Mean Platelet Volume (MPV): Average size of platelets; may indicate platelet production rate 3

• Neutrophil-to-Lymphocyte Ratio (NLR): Used as a marker of systemic inflammation 3

• Platelet-to-Lymphocyte Ratio (PLR): Another inflammatory marker 3

• Reticulocyte Count: Measures immature red blood cells; indicates bone marrow activity 2

Clinical Applications

• CBC is one of the most frequently ordered laboratory tests in medicine, with approximately 1800 CBCs ordered daily at some institutions 4

• Used to diagnose and monitor various conditions including anemia, infections, bleeding disorders, and malignancies 4

• Helps assess cardiovascular and metabolic disease risk through analysis of various components 3

• Essential for monitoring patients with hematologic disorders and evaluating response to treatments 2

• Critical component in the workup of many conditions including multiple myeloma 5, acute lymphoblastic leukemia 5, and myeloid/lymphoid neoplasms 5

Interpretation Considerations

• Results should be interpreted in the context of the patient's clinical presentation and other laboratory findings 4

• Abnormal results may require follow-up testing to determine the underlying cause 4

• Reference ranges may vary slightly between laboratories and by patient demographics 2