MEASUREMENT OF RED BLOOD CELL-VITAMIN-B12 - A STUDY OF THE CORRELATION BETWEEN INTRACELLULAR B12 CONTENT AND CONCENTRATIONS OF PLASMA HOLOTRANSCOBALAMIN-II

We have recently reported a new and rapid assay to measure plasma holo transcobalamin II (holoTC II) as a means of exploring vitamin B12 stat us. In order to further evaluate the significance of plasma holoTC II in determining tissue cobalamin, we have chosen the red blood cell-vit amin B12 (RBC-B12) assay as a measure of tissue vitamin B12 content an d studied the relationship between RBC-B12 and plasma holoTC II levels . Plasma holoTC II and RBC-B12 concentrations were concomitantly assay ed in 20 hematologically normal controls and cancer patients. In our g roups of controls, the mean value of RBC-B12 was determined as 241 +/- 51 pg/ml of packed erythrocytes (PE) with a range varying from 180 to 355 pg/ml PE. Preliminary results obtained in 32 cancer patients reve aled lower holoTC II and RBC-B12 levels than the control group and a r equired threshold value of 70 pg/ml of holoTC II in order to maintain a normal RBC-B12 greater than 180 pg/ml PE.