Neonatal Intensive Care Unit, "Agios Panteleimon" General Hospital of Nikea, Piraeus, Greece. Electronic address: sokourozeta@yahoo.gr. Neonatal Intensive Care Unit, "Agios Panteleimon" General Hospital of Nikea, Piraeus, Greece. Laboratory of Haematology and Blood Bank Unit, "Attiko" Hospital, School of Medicine, National and Kapodistrian University of Athens, Greece. Neonatal Department, National and Kapodistrian University of Athens, Aretaieio Hospital, Athens, Greece. Laboratory of Biomathematics, University of Thessaly School of Medicine, Larissa, Greece. Department of Biomedical Sciences, Humanitas University, Milan, Italy; IRCCS Humanitas Research Hospital, Milan, Italy. Laboratory of Biomathematics, University of Thessaly School of Medicine, Larissa, Greece; Department of Nephrology, University of Thessaly School of Medicine, Mezourlo, Larissa, Greece. Laboratory of Biomathematics, University of Thessaly School of Medicine, Larissa, Greece; Institute for Clinical Research and Health Policy Studies, Tufts Medical Center, Tufts University School of Medicine, Boston, USA.