Question

what is a functional test for b12 deficiency?
a) methylmalonic acid
b) d - xylose
c) schilling test
d) coombs test

Explanation:

• Methylmalonic acid (MMA) levels increase in vitamin B12 deficiency as B12 is a co - factor for the enzyme that metabolizes methylmalonyl - CoA. Elevated MMA is a functional test as it reflects the impaired metabolic function due to B12 lack.
• D - xylose test is for assessing intestinal absorption (e.g., in celiac disease), not specifically for B12 deficiency.
• The Schilling Test was previously used but is now less common due to radioactive material use.
• Coombs Test is for detecting antibodies on red blood cells (e.g., in autoimmune hemolytic anemia), not related to B12 deficiency.

Answer:

A. Methylmalonic acid