Calibration curves for the three assay formats of Fig. 3, and a comparison of prototype assay with HoloTC RIA. (A) Calibration curve for prototype assay using mAb 3C4 as capture ligand (format A). (B) Comparison of the prototype assay and HoloTC RIA for 15 serum samples ranging from 14 to 139 pmol/L as determined by HoloTC RIA. (C) Calibration curve for assay using mAb 3C4 as the detecting ligand (format B). (D) Calibration curve of assay for cobalamin TC saturation (format C).