[1] Katholieke Univ Leuven, Acad Ctr Gen Practice, Dept Publ Hlth & Primary Care, Leuven, Belgium
[2] Univ Liege, Dept Gen Practice, Res Unit Primary Care & Hlth, Liege, Belgium
[3] Katholieke Univ Leuven, Leuven Biostat & Stat Bioinformat Ctr L Biostat, Dept Publ Hlth & Primary Care, Leuven, Belgium
[4] Univ Antwerp, Dept Family Med & Populat Hlth, Antwerp, Belgium
[5] Univ Ghent, Ctr Family Med, Dept Publ Hlth & Primary Care, Ghent, Belgium
[6] Vrije Univ Brussel, Dept Family Med & Chron Care, Brussels, Belgium
[7] Univ libre Bruxelles, Dept Gen Practice, Brussels, Belgium
[8] Katholieke Univ Leuven, Acad Ctr Gen Practice, Dept Publ Hlth & Primary Care, Kapucijnenvoer 7,Box 7001, B-3000 Leuven, Belgium