1. Department of General Practice and Health Services Research, University Hospital Heidelberg, Im Neuenheimer Feld 130.3, 69120 Heidelberg, Germany
2. aQua Institute for Applied Quality Promotion and Research in Health Care GmbH, Maschmühlenweg 8-10, 37073 Göttingen, Germany
3. Institute of Medical Biometry, University Hospital Heidelberg, Im Neuenheimer Feld 130.3, 69120 Heidelberg, Germany