Pernicious anaemia is often used synonymously with vitamin B12 deficiency. However, pernicious anaemia specifically refers to anaemia resulting from vitamin B12 deficiency caused by an autoimmune metaplastic atrophic gastritis with loss of intrinsic factor (IF).
Patients with classic pernicious anaemia, most commonly younger adults, are at increased risk of stomach cancers and other gastrointestinal cancers. When clinical judgment suggests vitamin B12 deficiency but the vitamin B12 level is low-normal or hematologic indexes are normal, other tests have to be done.
After deficiency is diagnosed, additional tests may be indicated for younger adults but usually not for the elderly. Unless dietary vitamin B12 is obviously inadequate, measurement of serum gastrin levels or intrinsic factor antibodies may be done.