Multisite evaluation of a monoclonal IMMULITE erythropoietin immunoassay William E. Owen a , Geralyn Lambert-Messerlian b , Cabrini Delaney c , Robert Christenson d , Bertrand Plouffe e , Rocio Ludewig e , Anne Woods e , Jyh-Dar Lei e , Stephan Thompson e , William L. Roberts a,f , Joely A. Straseski a,f, ⁎ a ARUP Institute for Clinical and Experimental Pathology®, Salt Lake City, UT, USA b Women and Infants Hospital of Rhode Island, Providence, RI, USA c Quest Diagnostics, Valencia, CA, USA d University of Maryland School of Medicine, Baltimore, MD, USA e Siemens Healthcare Diagnostics Inc., Tarrytown, NY, USA f Department of Pathology, University of Utah Health Sciences Center, Salt Lake City, UT, USA abstract article info Article history: Received 19 September 2013 Received in revised form 14 November 2013 Accepted 17 November 2013 Available online 26 November 2013 Keywords: Method comparison Imprecision Interference Chemiluminescent immunoassay IMMULITE Serum erythropoietin Reference interval Background: Erythropoietin (EPO) measurements are useful in diagnosing anemias and polycythemias. We conducted a multisite evaluation of a monoclonal IMMULITE® EPO immunoassay. 1 Design and methods: The IMMULITE EPO assay is a solid-phase enzyme-labeled chemiluminescent immunometric assay. Method comparison to the Beckman ACCESS 2 assay using clinically characterized samples and reproducibility studies were conducted at three external independent laboratories. Internal evaluation conducted at Siemens included comparison of IMMULITE® 2000 and IMMULITE® 1000 assays to the ACCESS 2 assay; imprecision; linearity; limit of blank (LoB), limit of detection (LoD), and functional sensitivity; potential interference and cross-reactants; and reference interval determination. Results: External method comparison gave Deming regression of (IMMULITE 2000) = 0.96(ACCESS 2) + 2.57 IU/L, r = 0.98 (n = 217). Reproducibility ranged from 6.1% to 16.2%. Internal method comparisons gave Deming regressions of (IMMULITE 2000) = 1.09(ACCESS 2)-3.51 IU/L, r = 0.98 and (IMMULITE 1000) = 0.95(ACCESS 2) + 0.52 IU/L, r = 0.95. Total imprecision ranged from 6.4% to 10.3% and linearity was confirmed from 3.5 to 562 IU/L. LoB, LoD, and functional sensitivity were 0.5, 1.0, and 1.5 IU/L, respectively. The assay was highly specific for EPO. Nonparametric reference interval was 4.3 to 29.0 IU/L (n = 170). Conclusions: The monoclonal IMMULITE EPO assay showed acceptable performance for EPO measurement. © 2013 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved. Introduction Erythropoietin (EPO) is a 30 kDa highly glycosylated and acidic glycoprotein hormone comprised of 165 amino acids. EPO is primarily produced by the hepatocytes during fetal development, and postnatally by the peritubular cells of the renal cortex. EPO's primary role is to maintain red blood cell mass and hemoglobin at steady levels. There- fore, anemia and hypoxia are the main stimuli for the production of EPO. It binds to EPO receptors on the cell surface of the erythroid colony- forming unit and erythroid burst-forming units in the bone marrow to initiate erythropoiesis [1]. Anemia may occur if kidneys are damaged or unable to effectively respond to the demand for EPO, or if the patient's bone marrow stem cells do not respond to EPO stimulation. Hypoxia-induced expression of EPO has recently been attributed to activation of its promoter region by hypoxia-inducible-factor-2 [2]. Increased concentrations of EPO may be due to conditions of iron- deficiency, megaloblastic or hemolytic anemias, myelodysplasia, chemotherapy, acquired immunodeficiency syndrome (AIDS), renal cell or adrenal carcinoma pheochromocytoma; while decreased concen- trations may be associated with polycythemia vera and renal diseases [1,3]. Siemens has developed a monoclonal IMMULITE EPO assay using a one-step monoclonal–monoclonal sandwich format with a single 30 min incubation. The goal of this multisite study was to evaluate the overall analytical performance of the new IMMULITE EPO assay. Method comparison to the Beckman ACCESS 2 assay, reproducibility studies at three external independent laboratories, linearity, limit of blank (LoB), limit of detection (LoD), functional sensitivity, potential interference and cross-reactants, and reference interval determination for this immunoassay were all performed. Clinical Biochemistry 47 (2014) 216–219 Abbreviations: EPO, erythropoietin; LoB, limit of blank; LoD, limit of detection; CV, coefficient of variation. ⁎ Corresponding author at: c/o ARUP Laboratories, 500 Chipeta Way, Mail Code 115, Salt Lake City, UT 84108, USA. Fax: +1 801 584 5207. E-mail address: joely.a.straseski@aruplab.com (J.A. Straseski). 1 Not available for sale in the U.S. Product availability varies by country. 0009-9120/$ – see front matter © 2013 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.clinbiochem.2013.11.012 Contents lists available at ScienceDirect Clinical Biochemistry journal homepage: www.elsevier.com/locate/clinbiochem