Incidence and clinical significance of protein‐bound vitamin B12 malabsorption

Abstract

Patient records from January 1975 to December 1984 were analysed to assess the possible incidence of protein‐bound vitamin B₁₂ malabsorption. This condition is characterised by a low serum vitamin B₁₂ level and a normal Schilling test but impaired absorption of vitamin B₁₂ bound to protein. We found that 48 (25%) patients with a low serum cobalamin level unexplained by other causes had a normal Schilling test. Megaloblastic haemopoiesis was found in 25 of these. From this group, all 10 patients who had a test of protein‐bound vitamin B₁₂ absorption showed impaired absorption. Protein‐bound vitamin B₁₂ malabsorption may represent an early phase of pernicious anaemia when hypochlorhydria precedes intrinsic factor deficiency and should be tested for when the serum vitamin B₁₂ level is decreased and the Schilling test is normal.