Department of Clinical Chemistry, Erasmus MC, University Medical Center Rotterdam, P.O. Box 2040, 3000 CA, Rotterdam, The Netherlands. Department of Clinical Chemistry, Amsterdam Gastroenterology and Metabolism, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands. Department of Clinical Chemistry, Amsterdam Gastroenterology and Metabolism, Amsterdam UMC, Univ of Amsterdam, Amsterdam, The Netherlands. Department of Rheumatology, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands. Academic Center of Excellence - Inflammunity, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands. Department of Clinical Chemistry, Erasmus MC, University Medical Center Rotterdam, P.O. Box 2040, 3000 CA, Rotterdam, The Netherlands. s.heil@erasmusmc.nl. Academic Center of Excellence - Inflammunity, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands. s.heil@erasmusmc.nl.