title: Observational etiologic research: part 1--The etiologic research question: it requires DATA.
authors.affiliation: Center for Clinical Transfusion Research, Sanquin Research, Leiden, The Netherlands; Jon J. van Rood Center for Clinical Transfusion Research, Leiden University Medical Center, Leiden, The Netherlands; Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Rutger A
authors.initials: RA
authors.lastname: Middelburg
authors.forename: Johanna C
authors.initials: JC
authors.lastname: Wiersum-Osselton
authors.forename: Leo M G
authors.initials: LM
authors.lastname: van de Watering
authors.forename: Johanna G
authors.initials: JG
authors.lastname: van der Bom
mesh_terms: D035843:Biomedical Research; D001793:Blood Preservation; D004781:Environmental Exposure; D017707:Erythrocyte Transfusion; D006801:Humans; D013997:Time Factors