Response Factor–Based Quantification for Mycophenolic Acid

[摘要] To the Editor:In contrast with chemistry or immunoassay analyzers, quantification for liquid chromatography-tandem mass spectrometry (LC-MS/MS)1 assays is mostly done by time-consuming multipoint calibration in each run (CR) (1). Few reports on alternative quantification methods have been published, with most of them being impractical for clinical purposes (1–3) and none of them covering a large period of time (1–4). We evaluated the performance of quantification based on an experimentally derived response factor (RF) used for 1 year without change (4) for mycophenolic acid (MPA) compared to CR. We also examined the variables influencing RF quantification performance.MPA was extracted by protein precipitation using a reagent containing deuterated internal standard (IS) and analyzed on an Alliance HPLC 2795 separations module coupled to a Quattro Micro tandem MS (both Waters Corp.). From June 2012 to May 2013, the first 10 patient samples, QCs of each run, and external QCs were quantified by CR and RF. CR was performed using a weighted (1/ x ) linear regression of 7 calibrators. RF quantification was performed by multiplying the observed response ratio (RR) (area analyte/area IS) by …

[学科分类] 过敏症与临床免疫学