What is the optimal level of vitamin D in non-dialysis chronic kidney disease population? Pablo Molina, José L Górriz, Mariola D Molina, Sandra Beltrán, Belén Vizcaíno, Verónica Escudero, Julia Kanter, Ana I Ávila, Jordi Bover, Elvira Fernández, Javier Nieto, Secundino Cigarrán, Enrique Gruss, Gema Fernández-Juárez, Alberto Martínez-Castelao, Juan F Navarro-González, Ramón Romero, Luis M Pallardó Pablo Molina, Sandra Beltrán, Belén Vizcaíno, Verónica Escudero, Julia Kanter, Ana I Ávila, José L Górriz, Luis M Pallardó, Department of Nephrology, Dr Peset University Hospital, 46017 Valencia, Spain José L Górriz, Luis M Pallardó, Department of Medicine, Universitat de València, 46005 Valencia, Spain Mariola D Molina, Department of Mathematics, Universidad de Alicante, San Vicente del Raspeig, 03690 Alicante, Spain Jordi Bover, Department of Nephrology, Fundació Puigvert, 080348 Barcelona, Spain Elvira Fernández, Department of Nephrology, Hospital Uni- versitari de Lleida, IRBlleida (Institut de Reserca Biomèdica de Lleida), 25198 Lleida, Spain Javier Nieto, Department of Nephrology, Hospital General Universitario de Ciudad Real, 13005 Ciudad Real, Spain Secundino Cigarrán, Department of Nephrology, Hospital da Costa Burela, 7880 Lugo, Spain Enrique Gruss, Gema Fernández-Juárez, Department of Nephrology, Hospital Universitario Fundación Alcorcón, 28922 Madrid, Spain Alberto Martínez-Castelao, Department of Nephrology, Hospital Universitario de Beellvitge, IDIBELL, L’Hospitalet de Llobregat, 08907 Barcelona, Spain Juan F Navarro-González, Research Unit and Department of Nephrology, University Hospital Nuestra Señora de Candelaria, 38010 Santa Cruz de Tenerife, Spain Ramón Romero, Department of Medicine, Universitat Autònoma de Barcelona, 08193 Barcelona, Spain Author contributions: Molina P, Górriz JL and Pallardó LM drafted the manuscript, designed the research and supervised the study; Molina P and Molina MD performed statistical analysis; Beltrán S, Vizcaíno B, Escudero V, Kanter J, Ávila AI, Bover J, Fernández E, Nieto J, Cigarrán S, Gruss E, Fernández-Juárez G, Martínez-Castelao A and Navarro-González JF were involved with data collection, and assisted with data analysis; all authors read and approved the fnal manuscript. Supported by Abbott and the Spanish Society of Nephrology. Institutional review board statement: The study was revie- wed and approved by the Dr Peset Hospital Research Ethics Committee. Informed consent statement: All study participants, or their legal guardian, provided informed written consent prior to study enrollment. Confict-of-interest statement: Molina P, Górriz JL and Martínez- Castelao A have received honoraria for giving lectures and for consulting on advisory boards for Abbott. The others authors declare no confict of interest. Data sharing statement: No additional data are available. Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/ licenses/by-nc/4.0/ Manuscript source: Invited manuscript Correspondence to: Pablo Molina, MD, PhD, Department of Nephrology, Dr Peset University Hospital, Avda. Gaspar Aguilar, 90, 46017 Valencia, Spain. molina_pab@gva.es ORIGINAL ARTICLE 471 September 6, 2016|Volume 5|Issue 5| WJN|www.wjgnet.com World Journal of Nephrology WJN Submit a Manuscript: http://www.wjgnet.com/esps/ Help Desk: http://www.wjgnet.com/esps/helpdesk.aspx DOI: 10.5527/wjn.v5.i5.471 World J Nephrol 2016 September 6; 5(5): 471-481 ISSN 2220-6124 (online) © 2016 Baishideng Publishing Group Inc. All rights reserved. Prospective Study