To the Editor.—We read with interest the article by Carmel1 in the August issue of the Archives. He concluded that emphasis on very low cobalamin levels risks delaying the diagnosis of pernicious anemia in a significant proportion of cases, especially in those with or without macrocytosis.
In the article he describes in Table 2 a patient with pernicious anemia with a serum cobalamin level of 184 pmol/L, which is equivalent to 250 pg/mL (using a standard conversion from SI units [picomoles per liter] to current units [picograms per milliliter], 1.357× SI units = current units).
Therefore Carmel's listing of levels of 148 to 184 pmol/L as slightly low in Table 1 of the article are listed as normal values (201 to 250 pg/mL) in many laboratories, including our own.
In our laboratory, as well as in many standard reference values, 2 the normal range of serum cobalamin levels is
GROSS JS, LAMB JF. Low Serum Cobalamin Levels in Pernicious Anemia. Arch Intern Med. 1990;150(4):910. doi:10.1001/archinte.1990.00390160150032