16 Review Article Page 1 of 16 Ionized calcium: analytical challenges and clinical relevance Aghilès Hamroun1, Jean-David Pekar2, Arnaud Lionet1, Amjad Ghulam3, Patrice Maboudou2, Ambroise Mercier2, Thierry Brousseau2, Guillaume Grzych3,4, François Glowacki1,5 1CHU Lille, Service de Néphrologie, F-59000, Lille, France; 2CHU Lille, Biochimie Automatisée (UF-8832), Pôle de Biologie Pathologie Génétique, F-59000, Lille, France; 3CHU Lille, Service « Hormonologie, Métabolisme, Nutrition, Oncologie », Pôle de Biologie Pathologie Génétique, Lille, France; 4INSERM, U1011-EGID, Institut Pasteur de Lille, F-59000, Lille, France; 5EA 4483-IMPECS-IMPact of Environmental Chemicals on Human Health, Research Department, 59045, Lille, France Contributions: (I) Conception and design: G Grzych, JD Pekar, A Hamroun; (II) Administrative support: G Grzych, JD Pekar, A Hamroun; (III) Provision of study materials or patients: None; (IV) Collection and assembly of data: G Grzych, JD Pekar, A Hamroun; (V) Data analysis and interpretation: G Grzych, JD Pekar, A Hamroun; (VI) Manuscript writing: All authors; (VII) Final approval of manuscript: All authors. Correspondence to: Dr. Guillaume Grzych, MD, MSc. Laboratory of Biochemistry, Biology and Pathology Center, Lille University Hospital, Pr J. Leclercq Boulevard, 59037 Lille, France. Email:
[email protected]. Abstract: Calcium is a central electrolyte involved in many physiological functions commonly measured in clinical practice. Abnormal calcium levels are frequently found, and could have serious clinical consequences. The free form of calcium, also called ionized calcium, plays a determining role in the human body. Its measurement still remains limited by technical, analytical and financial constraints. To overcome these limits, many formulas have been developed to estimate the ionized calcium value.