LAUSR

BACKGROUND For mycophenolic acid (MPA), therapeutic drug monitoring (TDM) is an essential tool for dosage optimization in transplant recipients and autoimmune diseases. In China, a new commercial kit using an immunochromatographic assay (FICA) with a point-of-care testing (POCT) system was approved for TDM of MPA. However, corroboration between FICA and clinically used assays remains unknown. The authors evaluated MPA concentrations in heart transplant recipients obtained via FICA, high-performance liquid chromatography combined with tandem mass spectrometry (LC-MS/MS), and enzyme multiplied immunoassay technique (EMIT). METHODS Nine heart transplant recipients administered a single mycophenolate mofetil (MMF) dose and four administered multiple MMF doses were enrolled. MPA samples were collected before administration, and after 0.5, 1, 1.5, 2, 4, 6, 8, 10, and 12 h, and assessed by two immunoassays (EMIT, FICA) and LC-MS/MS. Consistency between methods was evaluated using Passing-Bablok regression and Bland-Altman analysis. RESULTS For Passing-Bablok regression between FICA and LC-MS/MS, FICA = 0.784 LC-MS/MS + 0.360 (95% CI slope: 0.739 to 0.829, 95% CI intercept: 0.174 to 0.545). Regardless of a significant observed correlation coefficient (R2= 0.9126), statistical analyses revealed a significant difference between FICA and the reference LC-MS/MS method. The mean absolute bias was 0.69 µg/mL between FICA and LC-MS/MS. Bland-Altman plots showed a mean bias of -0.23 µg/mL (± 1.96 SD, -2.19 to 1.72 ug/mL) and average relative bias of 14.73% (± 1.96 SD, -67.91 to 97.37%) between FICA and LC-MS/MS. Unsatisfactory consistency was observed between EMIT and LC-MS/MS, and FICA and EMIT. Differences between pharmacokinetic parameters after a single or 7 days of MMF administration, by LC-MS/MS and FICA, were not statistically significant. CONCLUSIONS The consistency of the new FICA using a POCT device with LC-MS/MS and EMIT was inadequate, and the accuracy of EMIT and LC-MS/MS was inappropriate. Clinicians should be informed when switching MPA detection methods to avoid misleading results.