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Evaluation of QMS Everolimus Assay Using Hitachi 917 Analyzer: Comparison With Liquid Chromatography/Mass Spectrometry

Dasgupta, Amitava PhD*; Davis, Bonnet MT(ASCP); Chow, Loretta MT(ASCP)

doi: 10.1097/FTD.0b013e31820afc97
Original Article
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Everolimus is an immunosuppressant requiring routine monitoring in whole blood. We evaluated the analytical performance of a new immunoassay for everolimus, Quantitative Microsphere System (QMS) everolimus (Thermo Fisher Scientific), which is CE marked and currently under review by Food and Drug Administration of the United States by comparing results with values obtained by using liquid chromatography/mass spectrometry. The total coefficient of variations (CVs) were 8.3% for low control (mean: 3.8 ng/mL), 6.1% for the medium control (mean: 8.0 ng/mL), and 7.5% for the high control (mean: 14.4 ng/mL) (n = 80 for each control, run over 20 nonconsecutive days). The respective total CVs for patients' pool were 13.3% (mean: 4.0 ng/mL), 7.5% (mean: 8.2 ng/mL), and 8.7% (mean: 11.7 ng/mL) (n = 80 for each patient pool). The assay was linear from a whole-blood everolimus level between 1.5 and 20 ng/mL, and the limit of quantitation was 1.3 ng/mL. Comparison was carried out using 90 renal transplant patient samples, and we observed the following Passing and Bablok linear regression plot: y = 1.11, slope = −0.005 (R2 = 0.92). This assay was not affected by commonly used 70 drugs, but sirolimus, a drug structurally similar to everolimus, showed 46% cross-reactivity. We conclude that QMS everolimus immunoassay has adequate sensitivity and specificity for the determination of whole-blood everolimus and can be used for routine therapeutic drug monitoring.

From the *Department of Pathology and Laboratory medicine, University of Texas Medical School in Houston and Laboratory Services; and †Memorial-Hermann Hospital at the Texas Medical Center, Houston, TX.

Received for publication November 11, 2010; accepted December 10, 2010.

This work was supported by a research contract from Thermo Fisher Scientific.

Correspondence: Amitava Dasgupta, PhD, Department of Pathology and Laboratory Medicine, University of Texas-Houston Medical School, 6431 Fannin, MSB 2.292 Houston, TX 77030 (e-mail: amitava.dasgupta@uth.tmc.edu).

© 2011 Lippincott Williams & Wilkins, Inc.