Evaluation of the EMIT Mycophenolic Acid Assay from Dade Behring.
The Emit Mycophenolic Acid Assay, a new homogeneous enzyme immunoassay for the quantitative analysis of mycophenolic acid (MPA) in human plasma, was evaluated and compared to a high-performance liquid chromatography (HPLC) method. Coefficients of variation (CV) of the within-run imprecision (n = 10) varied from 2.5% to 4.4% and from 1.3% to 4.9% for the Emit and the HPLC, respectively. The CV's of between-day imprecision (n = 10) ranged from 7.9% to 10.8% for the Emit and from 4.7% to 12.1% for the HPLC. Mean recoveries were 95.6% and 100.1% for Emit and HPLC, respectively. Serial dilution of a patient pool demonstrated a linear relationship between expected (x) and measured (y) concentrations: Emit, y = 0.998x + 0.086; HPLC, y = 1.006x - 0.016. The detection limit and the lower limit of quantification were 0.087 mg/L and 0.20 mg/L for Emit. The detection limit for HPLC was 0.08 mg/L using a signal-to-noise ratio of three. Sample stability under various storage conditions was satisfactory, although storage at -20 degrees C is recommended for storage longer than one day. No cross-reactivity from the major metabolite mycophenolic acid glucuronide (MPAG) was found. A correlation study on 261 patient samples yielded the following regression equation (bivariate Deming procedure): Emit = 1.012HPLC + 0.244, r = 0.970.
Vogl
M
M
Kaiser Franz Josef Hospital, Department of Laboratory Diagnostics and Ludwig Boltzmann Institute for Cardiosurgical Research, Vienna, Austria.
Weigel
G
G
Seebacher
G
G
Griesmacher
A
A
Laufer
G
G
Müller
M M
MM
D000328:Adult; D000368:Aged; D002851:Chromatography, High Pressure Liquid; D003429:Cross Reactions; D004355:Drug Stability; D017248:Enzyme Multiplied Immunoassay Technique; D020719:Glucuronides / Q000097:blood; D016027:Heart Transplantation; D006801:Humans; D007166:Immunosuppressive Agents / Q000097:blood*; D008875:Middle Aged; D009173:Mycophenolic Acid / Q000097:blood*; D012044:Regression Analysis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D020719:Glucuronides; D007166:Immunosuppressive Agents; D009173:Mycophenolic Acid