What is the diagnosis and management for an MCV of 79.5?

Microcytic Anemia: Diagnosis and Management for MCV 79.5 fL

An MCV of 79.5 fL indicates microcytic anemia, and you should immediately obtain iron studies (serum ferritin, transferrin saturation, serum iron, TIBC) along with a complete blood count with red cell distribution width (RDW) and peripheral blood smear to identify iron deficiency as the most likely cause. 1

Initial Diagnostic Workup

The diagnostic approach to microcytosis requires a systematic evaluation:

• Obtain iron studies immediately, including ferritin, transferrin saturation, serum iron, and total iron binding capacity (TIBC), as these are essential to diagnose iron deficiency—the most common cause of microcytosis 1

• Measure red cell distribution width (RDW) to help differentiate between causes of microcytosis, as elevated RDW suggests iron deficiency while normal RDW may indicate thalassemia trait 1

• Perform peripheral blood smear examination to evaluate red cell morphology for hypochromia, target cells, or other characteristic findings 1

• Include reticulocyte count to distinguish between decreased red blood cell production versus increased destruction 1, 2

Interpretation of Findings

The MCV of 79.5 fL falls below the normal range (typically 80-100 fL), indicating microcytosis rather than macrocytosis. While the provided evidence focuses primarily on macrocytosis, the diagnostic principles apply in reverse:

• Iron deficiency is the primary concern with an MCV below 80 fL, particularly if ferritin is low (<15-20 μg/L) and TIBC is elevated 1, 3

• MCH and MCHC values should be evaluated alongside MCV, though research shows these indices have only moderate diagnostic accuracy (AUC 0.68-0.96) for identifying iron deficiency 4

• Normal MCV does not exclude iron stores depletion, and conversely, microcytosis strongly suggests but does not definitively confirm iron deficiency without confirmatory testing 4

Common Pitfalls to Avoid

• Do not assume iron deficiency without confirmatory testing, as thalassemia trait, anemia of chronic disease, and lead toxicity can also cause microcytosis 1

• Concurrent iron deficiency can coexist with other conditions, so evaluate the complete clinical picture including inflammatory markers (CRP) if chronic disease is suspected 2

• In children and young adults, MCV cutoffs for diagnosing iron deficiency have approximately 90% sensitivity but only 50% specificity, meaning many patients with normal iron stores will have borderline low MCV 4

Management Algorithm

1. If ferritin <15-20 μg/L and elevated TIBC: Diagnose iron deficiency anemia and initiate oral iron supplementation (or parenteral iron if indicated) 1, 3

2. If ferritin normal but transferrin saturation <20%: Consider functional iron deficiency or early iron depletion 1

3. If iron studies are normal: Evaluate for thalassemia trait (hemoglobin electrophoresis), anemia of chronic disease (inflammatory markers), or lead exposure 1

4. Recheck CBC in 4-8 weeks after initiating iron therapy to confirm response, with expected improvement in hemoglobin and gradual normalization of MCV 3