Which test result most strongly supports a diagnosis of pernicious anemia?

Which test result most strongly supports a diagnosis of pernicious anemia?

• A. Positive anti-intrinsic factor antibodies
• B. Positive anti-dsDNA antibodies
• C. Low vitamin B12 with normal intrinsic factor antibodies
• D. Elevated homocysteine alone

Answer: (A)

Pernicious anemia is caused by autoimmune destruction affecting intrinsic factor, which is essential for vitamin B12 absorption. The most persuasive laboratory finding is antibodies directed against intrinsic factor. These autoantibodies specifically disrupt how intrinsic factor delivers B12 to the ileum, so their presence strongly supports pernicious anemia as the cause of B12 deficiency. Low vitamin B12 confirms the deficiency but doesn’t reveal the cause. Anti-dsDNA antibodies are associated with systemic autoimmune diseases like SLE and aren’t related to B12 absorption. Elevations in homocysteine can occur with B12 or folate deficiency but don’t identify the underlying mechanism, so they’re not as diagnostic for pernicious anemia.

Pernicious anemia is caused by autoimmune destruction affecting intrinsic factor, which is essential for vitamin B12 absorption. The most persuasive laboratory finding is antibodies directed against intrinsic factor. These autoantibodies specifically disrupt how intrinsic factor delivers B12 to the ileum, so their presence strongly supports pernicious anemia as the cause of B12 deficiency.

Low vitamin B12 confirms the deficiency but doesn’t reveal the cause. Anti-dsDNA antibodies are associated with systemic autoimmune diseases like SLE and aren’t related to B12 absorption. Elevations in homocysteine can occur with B12 or folate deficiency but don’t identify the underlying mechanism, so they’re not as diagnostic for pernicious anemia.