Department of Epidemiology and Biostatistics, VU University Medical Center, De Boelelaan 1089a, HV Amsterdam, 1081, The Netherlands. r.menezes@vumc.nl.|Department of Statistics, Shiraz University, Shiraz, Iran. mohammadileila@yahoo.com.|Biostatistics, Department for Health Evidence, Radboud University Medical Center, Nijmegen, The Netherlands. jelle.goeman@radboudumc.nl.|Department of Pediatric Oncology and Hematology, Erasmus MC-Sophia Childrens Hospital, Rotterdam, The Netherlands. j.m.boer@erasmusmc.nl.