1 Department of internal medicine, Amsterdam VU University Medical Center, Amsterdam, The Netherlands. Electronic address: jj.vandiemen@vumc.nl.
2 Department of internal medicine, Amsterdam VU University Medical Center, Amsterdam, The Netherlands.
3 Department of Public Health & Primary Care, Leiden University Medical Center, Leiden, The Netherlands.
4 Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, The Netherlands; JJ van Rood Center for Clinical Transfusion Research, Sanquin Research, Leiden, The Netherlands.