[1] MUMC, Sch Publ Hlth & Primary Care CAPHRI, Dept Paediat Pulmonol, NL-6202 AZ Maastricht, Netherlands
[2] MUMC, Dept Clin Epidemiol & Med Technol Assessment, NL-6229 HX Maastricht, Netherlands
[3] MUMC, CAPHRI, Dept Methodol & Stat, NL-6229 HA Maastricht, Netherlands
[4] Zuyderland Med Ctr, Dept Paediat, NL-6162 BG Sittard Geleen, Netherlands
[5] MUMC, CAPHRI, Dept Primary Care Med, NL-6229 HA Maastricht, Netherlands