“…Of these, 53.8% were institutionally based [12,19,[48][49][50][51], 30.8% were study-specific [19,29,46,51] and 23.1% were national or international guidelines [12,14,16]. The majority (76.9%) specified a minimal age, ranging from 4 to 12 years, above which assent should be obtained [14,16,19,46,[48][49][50][51]. The majority of the studies referred to North American (61.5%) [12,19,46,[48][49][50][51] and European guidelines (38.5%) [12,14,16,29,46].…”