1. ECAT Foundation (External Quality Control for Assays and Tests) , Voorschoten , The Netherlands
2. Department of Medical Biochemistry and Pharmacology , Haukeland University Hospital , Bergen , Norway
3. Norwegian Organization for Quality Improvement of Laboratory Examinations (Noklus) , Haraldsplass Deaconess Hospital , Bergen , Norway
4. Result Laboratory , Amphia Hospital , Breda , The Netherlands
5. European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) Working Group on Biological Variation and Task Group for the Biological Variation Database , Milan , Italy
6. Department of Hematology, Erasmus MC , University Medical Center Rotterdam , Rotterdam , The Netherlands