Author contributions An expert meeting was organized by PEV, RJMB, JW and FLvdV and held in Amsterdam on April 16, 2019. Present at the expert meeting were PEV, BJAR, RJMB, SB, CJC, OAC, DRG, NAFJ, BJK, KL, JM, MHN, TFP, TRR and FLvdV. A first draft manuscript was prepared by PEV, BJAR, RJMB, JW and FLvdV and circulated for comments from all experts. All experts reviewed and commented on the manuscript. Using these comments, a final version was circulated for approval.