Measurement of Serum Vitamin B₁₂ Level Using Radioisotope Dilution and Coated Charcoal

A method for measurement of serum B₁₂ level using radioisotope dilution and charcoal coated with albumin or hemoglobin is presented. Its advantages over previously described radioisotopic methods and the classical bioassay procedure are greater simplicity, rapidity and reproducibility. The sensitivity range appears to extend from the lowest to the highest B₁₂ values of normal and pathologic sera. The materials for the assay are readily available and the procedure can be completed within an hour. The assay can be applied to other biologic fluids and materials and also readily adopted for routine use by any clinical laboratory equipped to use radioisotopes.