RBC indices interpretation


The table below is a quick summary of how changes in the mean cell volume (MCV) and mean cell hemoglobin concentration (MCHC) can guide us as to the mechanism and potential cause of an anemia.

How red blood cell indices helps with identifying mechanism and cause of an anemia
MCV MCHC Severity Regenerative? Mechanism Potential causes
Normocytic Normochromic Mild to moderate No Decreased production Anemia of inflammatory disease (most common; due to inflammatory cytokines which suppress erythropoiesis and sequester iron via increasing hepcidin; many diseases including neoplasia, inflammation, liver disease), chronic renal disease (decreased erythropoietin), endocrine disease (hypothyroidism, hypoadrenocorticism), ineffective hematopoiesis (infectious agents, e.g. Ehrlichia canis, drugs, histiocytic sarcoma, lymphoma, immune-mediated), severe nutritional deficiencies.
Normocytic Normochromic Severe No Decreased production Primary bone marrow problem (e.g. non-regenerative immune-mediated anemia, pure red blood cell aplasia, or precursor directed immune-mediated anemia [PIMA], hematopoietic neoplasia, infiltrative neoplasia, bone marrow aplasia), drugs (e.g. immune response against erythropoietin therapy, idiosyncratic drug reaction), some forms of chronic renal disease (particularly congenital disorders), multifactorial anemia (more than one mechanism).May or may not be accompanied by other cytopenias (neutropenia, thrombocytopenia).
Normocytic Normochromic Any Yes Hemorrhage or hemolysis Many causes
Macrocytic Normochromic to hypochromic Any No Decreased production with abnormal DNA metabolism Vitamin B12 deficiency, folate deficiency, cobalt deficiency (molybdenum excess), feline leukemia virus infection in cats, congenital dyserythropoietic anemia, myelodysplastic syndrome, drugs that interfere with DNA metabolism (e.g. hydroxyurea), non-regenerative immune-mediated anemia (precursor directed immune mediated anemia, PIMA), inherited defects in RBC membrane (hereditary stomatocytosis)
Macrocytic Hypochromic Any Yes Hemorrhage or hemolysis Many causes of hemorrhage or hemolysis. Regeneration may be mild in some causes.
Microcytic Normochromic to hypochromic Any No Decreased production with defective hemoglobin production Iron deficiency, copper deficiency (zinc excess, rare), vitamin B6 deficiency (experimental), portosystemic shunts (frequently not anemic), congenital dyserythropoiesis (English Springer Spaniels), band 4.1 deficiency with hereditary elliptocytosis (dog), drugs or toxins that interfere with hemoglobin production (e.g. chronic lead poisoning), PIMA.
Microcytic Hypochromic Any Yes Iron deficiency Chronic external blood loss, nutritional iron deficiency, copper deficiency (zinc excess).