title: Positive bias in mycophenolic acid concentrations determined by the CEDIA assay compared to HPLC-UV method: is CEDIA assay suitable for therapeutic drug monitoring of mycophenolic acid?
abstract: BACKGROUND
  Both immunoassays and chromatographic methods are available for therapeutic drug monitoring of mycophenolic acid (MPA), an immunosuppressant. We studied the suitability of cloned enzyme donor immunoassay (CEDIA) assay for routine monitoring of MPA by comparing values obtained by the CEDIA assay with corresponding values obtained by using a high-performance liquid chromatography combined with ultraviolet detection (HPLC-UV) method.
  
  
  METHODS
  We compared MPA concentrations obtained by a reference HPLC-UV method and CEDIA assay on Hitachi 917 analyzer (Roche Diagnostics, Indianapolis, IN) using 60 patient specimens (18 liver transplant recipient and 42 kidney transplant recipients).
  
  
  RESULTS
  When MPA concentrations in all 60 transplant recipients obtained by the HPLC-UV (x-axis) method were compared with corresponding values obtained by the CEDIA method (y-axis), the following regression equation was obtained: y = 1.1558x + 0.2876 (r = 0.97). Interestingly, much lower bias was observed in 42 renal transplant recipients as revealed by the following regression equation; y = 1.1181x + 0.2745 (r = 0.98). However, more significant positive bias was observed in 18 liver transplant recipients as following regression equation as observed: y = 1.3337x + 0.1493 (r = 0.94).
  
  
  CONCLUSIONS
  We conclude that MPA concentrations determined by the CEDIA assay showed significant positive bias compared to HPLC-UV method. Therefore, caution must be exercised in interpreting therapeutic drug monitoring result of MPA if CEDIA assay is used.
authors: Department of Pathology, University of Texas-Houston Medical School and Laboratory Services Memorial-Hermann Hospital at Texas Medical Center, Houston, TX, USA. Amitava.Dasgupta@uth.tmc.edu
authors: Amitava
authors: A
authors: Dasgupta
authors: Myrtle
authors: M
authors: Johnson
mesh_terms: D015982:Bias; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D016903:Drug Monitoring / Q000379:methods*; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods*; D016030:Kidney Transplantation; D057230:Limit of Detection; D016014:Linear Models; D016031:Liver Transplantation; D009173:Mycophenolic Acid / Q000097:blood*; D015203:Reproducibility of Results
chemical_list: D009173:Mycophenolic Acid