From the Guidelines
The initial step in the workup of a patient with macrocytic anemia is to obtain a complete blood count (CBC) with peripheral smear, serum vitamin B12 level, and folate level, as these tests can help identify the underlying cause of the macrocytosis, with vitamin B12 and folate deficiencies being common causes of macrocytic anemia. According to the most recent guideline, measuring folic acid status is recommended at least once at first assessment and repeated within 3 months after supplementation to verify normalization 1.
When evaluating a patient with macrocytic anemia, it is essential to consider the potential causes, including vitamin B12 and folate deficiency, which can be treated with supplementation 1. The diagnosis of macrocytic anemia is typically made based on a mean corpuscular volume (MCV) greater than 100 fL, and a peripheral blood smear can reveal characteristic findings such as hypersegmented neutrophils in vitamin B12 or folate deficiency.
Some key points to consider in the workup of macrocytic anemia include:
- Measuring vitamin B12 and folate levels to identify deficiencies, which are common causes of macrocytic anemia 1
- Obtaining a peripheral blood smear to look for characteristic findings such as hypersegmented neutrophils 1
- Considering other potential causes of macrocytic anemia, such as liver disease or hypothyroidism
- Repeating folic acid status measurement within 3 months after supplementation to verify normalization 1
In terms of treatment, vitamin B12 deficiency should be treated immediately with hydroxocobalamin 1 mg intramuscularly, and folic acid deficiency should be treated with oral folic acid 5 mg daily for a minimum of 4 months 1. It is crucial to prioritize the treatment of vitamin B12 deficiency, as folic acid supplementation may mask severe vitamin B12 depletion 1.
From the Research
Initial Step in Workup of Macrocytic Anemia
The initial step in the workup of a patient with macrocytic anemia involves:
- A carefully obtained history and examination
- Evaluation of a peripheral blood smear and reticulocyte count 2
- Differentiation of megaloblastic and non-megaloblastic macrocytic anemias based on clinical information, patient history, and physical examination findings 3
Laboratory Testing
Laboratory testing may include:
- Serum vitamin B12 and folate levels to identify deficiencies 2, 4, 5
- Serum thyroid studies to rule out hypothyroidism 2
- Liver function studies to evaluate liver disease 2
- Bone marrow aspirate and biopsy with cytogenetic analysis to confirm a diagnosis suspected on the basis of the initial evaluation 2
Causes of Macrocytic Anemia
The most common causes of macrocytic anemias in adults are: