What does an elevated MCV and MCH indicate and how is it treated?

Elevated MCV and MCH: Diagnostic Approach and Treatment

Elevated MCV (103.5 fL) and MCH (35.1) indicate macrocytosis, which requires investigation for underlying causes including vitamin B12 deficiency, folate deficiency, medication effects, alcohol use, liver disease, or myelodysplastic syndrome. 1, 2

Diagnostic Approach

Initial Assessment

• Macrocytosis (MCV >100 fL) and elevated MCH are important indicators that warrant further investigation even in the absence of anemia 3, 2
• The kinetic approach to evaluating macrocytosis should include reticulocyte count to distinguish between decreased production and increased destruction of RBCs 1

Laboratory Workup

• Vitamin B12 levels should be measured, as deficiency is a common cause of macrocytosis 4, 2
• Serum and erythrocyte folate levels should be assessed, as folate deficiency can cause macrocytosis with normal B12 levels 2, 3
• Iron studies (ferritin, transferrin saturation, serum iron, TIBC) to rule out concurrent iron deficiency 1
• Liver function tests to evaluate for liver disease 5, 2
• Thyroid function tests to rule out hypothyroidism 2
• Red cell distribution width (RDW) can help differentiate causes of macrocytosis 1, 6

Additional Considerations

• Medication review is essential, as drugs like azathioprine, methotrexate, and anticonvulsants can cause macrocytosis 7, 2
• Alcohol consumption history should be obtained, as chronic alcohol use is a common cause of macrocytosis 5, 2
• Peripheral blood smear examination to evaluate red cell morphology 1
• Homocysteine levels may provide additional information on tissue deficiency of B12 or folate 2

Treatment Based on Underlying Cause

Vitamin B12 Deficiency

• For pernicious anemia: Intramuscular cyanocobalamin 100 mcg daily for 6-7 days, then alternate days for 7 doses, then every 3-4 days for 2-3 weeks, followed by 100 mcg monthly for life 8
• For patients with normal intestinal absorption: Oral B12 supplementation may be sufficient after initial parenteral treatment 8

Folate Deficiency

• Oral folate supplementation (typically 1-5 mg daily) 2, 3
• Address underlying causes of folate deficiency (malabsorption, increased requirements, dietary insufficiency) 3

Medication-Induced Macrocytosis

• Consider discontinuation or dose adjustment of offending medications, particularly if myelodysplastic changes are present 7
• Immediate discontinuation of azathioprine is recommended if myelodysplastic syndrome is suspected 7

Alcohol-Related Macrocytosis

• Alcohol cessation is the primary intervention 5, 2
• Nutritional supplementation including B vitamins 5

Liver Disease

• Management of underlying liver condition 5
• Supportive care and nutritional supplementation 2

Myelodysplastic Syndrome

• Hematology referral for bone marrow biopsy if suspected 7
• Treatment depends on MDS subtype and risk stratification 7

Monitoring

• Follow-up complete blood count to assess response to treatment 1, 6
• Periodic monitoring of vitamin levels in patients requiring long-term supplementation 8
• RDW can be used to monitor response to treatment, with sensitivity of 62.5-75% for detecting various deficiencies 6

Important Caveats

• MCV alone has poor sensitivity (17-30%) for detecting vitamin B12 deficiency in randomly screened populations; therefore, normal MCV does not rule out deficiency 4
• Macrocytosis may precede anemia and can be the earliest indicator of nutritional deficiencies 3
• Concurrent iron deficiency can mask macrocytosis by lowering MCV 1, 6
• In patients with inflammatory bowel disease, macrocytosis may indicate medication effects rather than nutritional deficiency 1, 7