Spurious Elevations of Vitamin B₁₂with Pernicious Anemia

To the Editor: Within a 3-week period, two women, 46 and 48 years of age, presented with peripheral neuropathy and associated pancytopenia with macrocytic anemia. Clinical suspicion for pernicious anemia was high, but vitamin B12 levels were 1644 pg per milliliter (1228 pmol per liter) and 1321 pg per milliliter (975 pmol per liter), respectively (reference range, 246 to 1320 pg per milliliter [181 to 974 pmol per liter]). On subsequent bone-marrow evaluation, specimens from both patients showed profound megaloblastic features. Additional findings on laboratory tests included elevated levels of homocysteine and methylmalonic acid combined with detection of intrinsic . . .