Pathophysiology
Clinical meaning
The complete blood count (CBC) evaluates three cell lines produced by bone marrow hematopoiesis from pluripotent stem cells. The RBC lineage is assessed by hemoglobin (Hgb), hematocrit (Hct), MCV (mean corpuscular volume classifying anemias as microcytic <80 fL, normocytic 80-100 fL, or macrocytic >100 fL), MCH, MCHC, RDW (red cell distribution width indicating anisocytosis), and reticulocyte count (reflecting marrow response). The WBC lineage includes neutrophils (bacterial infection, first responders), lymphocytes (viral infection, adaptive immunity), monocytes (chronic inflammation, phagocytosis), eosinophils (parasites and allergies), and basophils (hypersensitivity). Platelets (thrombocytes) are megakaryocyte fragments essential for primary hemostasis; the MPV (mean platelet volume) helps differentiate causes of thrombocytopenia (large platelets suggest peripheral destruction; small platelets suggest underproduction).