European Biological Variation Study (EuBIVAS): Within- and Between-Subject Biological Variation Data for 15 Frequently Measured Proteins Anna Carobene, 1,2 Aasne K. Aarsand, 2,3,4 Elena Guerra, 1 William A. Bartlett, 2,5 Abdurrahman Cos ¸kun, 2,6 Jorge Dı ´az-Garzo ´ n, 2,7 Pilar Fernandez-Calle, 2,7 Niels Jonker, 2,8 Massimo Locatelli, 1 Sverre Sandberg, 2,3,4,9 and Ferruccio Ceriotti 10* on behalf of the European Federation of Clinical Chemistry and Laboratory Medicine Working Group on Biological Variation BACKGROUND: The European Biological Variation Study (EuBIVAS) was established to deliver rigorously determined data for biological variation (BV). Here, EuBIVAS-based BV estimates are provided for  1 -acid glycoprotein,  1 - antitrypsin, albumin,  2 -microglobulin, ceruloplasmin, complement component 3, complement component 4, C-reactive protein (CRP), cystatin C, haptoglobin, IgA, IgG, IgM, soluble transferrin receptor (sTfR), and transfer- rin (Trf), together with their associated analytical perfor- mance specifications (APSs) and reference change values (RCVs). METHOD: Serum samples from weekly blood samplings of 91 healthy study participants (38 males and 53 fe- males, ages 21– 69 years old) over 10 consecutive weeks in 6 European laboratories were stored at -80 °C before duplicate analysis on a Roche Cobas c702. Outlier and variance homogeneity analyses were performed followed by CV-ANOVA on trend-corrected data if relevant, to determine BV and analytical variation estimates with CI and the associated RCV. RESULTS: For the acute phase proteins, several partici- pants experienced mild inflammatory episodes during the study, requiring exclusion of 7% of the 25 290 results. Within-subject BV (CV I ) estimates for specific proteins obtained in our study were lower than those available in the online 2014 BV database, except for Trf, whereas between-subject BV (CV G ) estimates were similar. CV I and CV G estimates for sTfR, which have not previously been published, were 6.0% and 19.1%, respectively. CONCLUSIONS: In addition to new BV estimates for sTfR, this EuBIVAS substudy generated more demanding APS for frequently requested plasma specific proteins. APS for CRP should not be calculated from BV data except when CRP is used as a risk factor for cardiovascular disease. © 2019 American Association for Clinical Chemistry Specific proteins serve as valuable markers for various diseases and are routinely measured in clinical laborato- ries by fully automated systems. For safe diagnostics and monitoring using these markers, it is important to ensure an analytical quality in line with clinical needs (1). In the First Strategic Conference of the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM), 11 3 models for setting analytical performance specifications (APSs) were established based on (a) the effect on clinical outcome, (b) biological variation (BV) data, and (c) the state of the art (2). The EFLM Task and Finish Group on Allocation of Laboratory Tests to Different Models for Performance Specifications proposed that a clinical out- come model should be applied if a measurand plays a central role in diagnosis or prognosis of a pathological status. Based on these principles, serum albumin and C-reactive protein (CRP) are suggested to be assigned to 1 Laboratory Medicine, Ospedale San Raffaele, Milan, Italy; 2 Biological Variation Working Group, European Federation of Clinical Chemistry and Laboratory Medicine, Milan, Italy http://efcclm.eu/science/wg-biological-variation; 3 Department of Medical Biochemistry and Clinical Pharmacology, Haukeland University Hospital, Bergen, Norway; 4 Norwegian Quality Improvement of Laboratory Examinations (Noklus), Haraldsplass Deaconess Hospital, Ber- gen, Norway; 5 Blood Sciences, Ninewells Hospital and Medical School, Scotland, UK; 6 Aciba- dem Mehmet Ali Aydinlar University, School of Medicine, Atasehir, Istanbul, Turkey; 7 Hospi- tal Universitario La Paz, Madrid, Spain, and Quality Analytical Commission of Spanish Society of Clinical Chemistry (SEQC); 8 Certe, Wilhelmina Ziekenhuis Assen, Assen, the Netherlands; 9 Department of Global Public Health and Primary Care, University of Bergen, Bergen, Nor- way; 10 Clinical Laboratory, Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico, Milan, Italy. * Address correspondence to this author at: Clinical Laboratory Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico, Via San Barnaba 8, 20122 Milan, Italy. E-mail ferruccio.ceriotti@policlinico.mi.it. Received March 14, 2019; accepted May 13, 2019. Previously published online at DOI: 10.1373/clinchem.2019.304618 © 2019 American Association for Clinical Chemistry 11 Nonstandard abbreviations: EFLM, European Federation of Clinical Chemistry and Lab- oratory Medicine; APS, analytical performance specification; BV, biological variation; CRP, C-reactive protein; CV I, within-subject biological variation; CV G , between-subject biological variation; EuBIVAS, European Biological Variation Study; AAT, 1-antitrypsin; AGP, 1-acid glycoprotein; 2M, 2-microglobulin; C3, complement component 3; C4, complement component 4; CysC, cystatin C; Trf, transferrin; sTfR, soluble transferrin receptor; RCV, reference change value; CV A , analytical variation; CV APS , analytical per- formance specification for imprecision; B APS , analytical performance specification for bias. Clinical Chemistry 65:8 000 – 000 (2019) Proteomics and Protein Markers 1 http://clinchem.aaccjnls.org/cgi/doi/10.1373/clinchem.2019.304618 The latest version is at Papers in Press. Published June 6, 2019 as doi:10.1373/clinchem.2019.304618 Copyright (C) 2019 by The American Association for Clinical Chemistry