1. Medical Microbiology and Immunology, Diakonessenhuis , Utrecht , The Netherlands
2. Microvida Laboratory of Medical Microbiology and Immunology , Elisabeth-TweeSteden Ziekenhuis , Tilburg , The Netherlands
3. Department of Hematology and Clinical Chemistry Laboratory , OLVG Lab , Amsterdam , The Netherlands
4. Department of Quality of Laboratories , Sciensano , Brussel , Belgium
5. Department of Epidemiology , External Quality Assessment Unit Nacional Institute of Health, Doctor Ricardo Jorge , Lisbon , Portugal
6. Labquality , Helsinki , Finland
7. Department of Laboratory Medicine , Radboud University Medical Centre , Nijmegen , The Netherlands
8. Foundation for Quality Assurance in Laboratory Medicine (SKML) , Nijmegen , The Netherlands
9. Department of Clinical Chemistry , Queen Beatrix Hospital , Winterswijk , The Netherlands