This study compares cyclosporin A (CsA) concentrations in plasma from patients receiving various transplants, as measured by HPLC and RIA with a monoclonal antibody for CsA and an 125I-labeled ligand. The RIA was restandardized with in-house standards because it overestimated CsA by an average of 23%. The RIA was sensitive to 2 micrograms/L, the standard curve was linear from 20 to 500 micrograms of CsA per liter, analytical recovery was 98%, and CVs were less than 8% for intra- and interassay precision. RIA (y) vs HPLC (x) for 283 plasma samples from 145 patients gave a slope = 1.1256, r = 0.979. When the results were segregated according to transplant type, CsA in liver and heart recipients was overestimated by RIA as compared with HPLC: slope = 1.202, r = 0.973 and slope = 1.1477, r = 0.983, respectively. Adult and pediatric CsA values were acceptable when RIA and HPLC were compared: slope = 1.0755, r = 0.977 and slope = 1.0563, r = 0.980, respectively. For six samples (four heart, two liver recipients) where HPLC and RIA values demonstrated wide discrepancies, repeat HPLC and analysis of eluate fractions gave CsA concentrations nearer values by the initial HPLC assay. We conclude that this RIA cannot be substituted for HPLC in the case of heart and liver recipients. The need for each laboratory to standardize the RIA is obvious.

A rapid liquid-chromatographic method is described for simultaneously determining prednisone, prednisolone, and cortisol in plasma. Before chromatography, samples containing an internal standard (methylprednisolone) were extracted with use of Chem Elut (Analytichem) columns. After elution of the glucocorticosteroids, the eluates were dried and reconstituted in a mobile phase of tetrahydrofuran/water (25/75 by vol). Samples were injected onto a reversed-phase C18 column, and analysis time was 15.5 min. Measures of analytical performance were all acceptable, and the method was used to assess noncompliance in pediatric renal-transplant recipients who were receiving prednisone and cyclosporine. Of the 37 pediatric patients tested, five (13.5%) were identified as noncompliant. The method is simple, accurate, and precise, and other steroids and medications commonly given to transplant recipients do not interfere with it.