Plasma cobalamin-binding and serum cobalamin in patients with folate deficiency

Plasma unsaturated R-binder and transcobalamin 2 (TC 2) levels were measured in 62 patients with folate deficiency and compared with 80 control subjects and 52 patients with pernicious anaemia. An increase in unsaturated R-binder concentration was found in the majority of patients with folate deficiency and with PA. In folate deficiency, however, the unsaturated R-binder was often elevated whether the serum cobalamin (Cbl) was low or normal, more frequently when the serum Cbl was normal. Results of a separate in vivo study of plasma retention of injected 57Co cyanocobalamin were consistent with these findings. An elevated TC2 was found in a small number of patients with folate deficiency and with PA. The serum Cbl appears to the maintained at a normal level in some patients with folate deficiency by an increase in R-binder, which is caused by folate deficiency itself.