Procedure
The investigation was conducted on a voluntary, confidential, and
anonymous basis, and the participants could withdraw at any time during
the study. In each of the 4 hospitals, two specially trained nurses were
appointed to conduct face-to-face investigations of the participants.
The questionnaires were completed by the participants in a quiet and
private room. For children with difficulties in reading or
comprehension, the investigators assisted them to complete the
questionnaire on the basis that they fully understood the content and
made their own decisions for each item. Before collection of the
questionnaires, the participants were asked to re-check for omissions.