Hematology and Oncology MOC Sample Questions

The correct answer is E. Serum methylmalonic acid and homocysteine levels

Explanation: Serum methylmalonic acid and homocysteine levels. TRUE: This patient has clinical findings suggestive of vitamin B12 deficiency (e.g. macrocytic anemia, neurologic symptoms, strict vegan diet) with borderline serum B12. In this case, checking the levels of metabolic intermediates methylmalonic acid and homocysteine can confirm the diagnosis. Both intermediates will be increased due to their accumulation in the context of vitamin B12 deficiency. (Only homocysteine will be elevated in folate deficiency). If a diagnosis of vitamin B12 deficiency is confirmed, a search for the cause would be pursued next. In this case, the patient’s strict vegan diet is the most likely reason.

Electromyelography and nerve conduction studies. FALSE: Although electromyelography and nerve conduction studies would confirm the presence of a neuropathy, they would not provide the necessary information to determine the etiology.

Computed tomography of lumbosacral spine. FALSE: Computed tomography of the lumbosacral spine could be required if other etiologies are excluded.

Therapeutic trial of vitamin B12. FALSE: The patient’s vitamin B12 and folate levels are best described as borderline. Thus, providing a therapeutic trial of B12 without first establishing the cause of the neurological symptoms would not be the most appropriate intervention at this point.

Bone marrow examination. FALSE: The lack of any other associated cellular abnormalities in the complete blood count and peripheral blood smear would render a bone marrow evaluation unnecessary at this time. Less invasive testing (e.g. serum metabolite intermediates) is most likely to reveal the etiology.