[1] Goethe Univ Frankfurt, Inst Gen Practice, Theodor Stern Kai 7, D-60590 Frankfurt, Germany
[2] Dept Hlth Econ & Hlth Care Management, Univ Str 25, D-33615 Bielefeld, Germany
[3] Vandage GmbH, Detmolder Str 30, D-33604 Bielefeld, Germany
[4] Maastricht Univ, Dept Family Med, POB 616, NL-6200 MD Maastricht, Netherlands
[5] Univ Bielefeld, Med Fac OWL, Dept Gen Practice & Family Med, Univ Str 25, D-33615 Bielefeld, Germany