1. Laboratory of Experimental Medicine, Université Libre de Bruxelles, 808 Route de Lennik, B-1070, Brussels, Belgium, Molecular Diagnostic Laboratory, Department of Clinical Biochemistry, Aarhus University Hospital, Skejby, Aarhus N, Denmark, and Division of Pulmonary Sciences and Critical Care Medicine and Biochemical Mass Spectrometric Facility, University of Colorado Health Sciences Center, Denver, CO, USA