Diagnosis of Megaloblastic Anemia

Diagnostic Tests Serum Cobalamine: Uses ELISA assay Normal Range: 118 – 148 pmol/L Cobalamine Deficiency: < 74 pmol/L Serum methylmalonate and Homocysteine Schilling Test Test for urinary excretion Studies absorption of Cobalamin Schilling Test: Patient fasts over night. Radioactive cyanocobalamin given orally. 2 hours later an IM injection of cyanocobalamin of 1 mg is given. A 24 h urine specimen is collected for determination of radioactivity; low excretion shows malabsoption; the oral dose is then given again after 48 hours with IF. Results distinguish between gastric and intestinal causes of cobalamin malabsorption.

Diagnostic Tests Serum Folate Red Cell Folate: Uses ELISA Normal range: 11 nmol/L to 82 nmol/L Can be elevated from severe cobalamin deficency Red Cell Folate: Valuable test for body folate stores. Less affected than serum assay by diet and traces of hemolysis. Normal adult conc.: 160-640 micrograms/L Subnormal levels occur in patients with Megaloblastic Anemia due to folate deficiency but also in nearly 2/3 of patient with severe cobalamine deficiency.

Treatment of Megaloblastic Anemia

Treatment Establish if it is a folate or cobalamine deficiency. In patients who are severely ill, it may be necessary to treat with both vitamins in large doses Transfusion is usually unnecessary and inadvisable.

Treatment of Cobalamine Deficiency Hydroxocobalamine Six 1000 micrograms IM injections given at 3-7 day intervals should replenish body stores. For maintenance therapy 1000 micrograms IM injection every three months. Cyanocobalamin Large daily oral doses (1000-2000 micrograms)

Treatment of Folate Deficiency Folic Acid Oral doses of 5-15 mg daily. Continue therapy for 4 months Cobalamine Deficincy must be excluded before large doses are given, otherwise cobalamine neuropathy may develop Folinic Acid A stable form of fully reduced folate. Given orally or parenterally to overcome toxic effects of methotrexate or other DHF reductase inhibitors.