Approval for the study was obtained from the hospital ethics committees. To identify potential subjects, the research student approach to eligible children and their parents after screening the medical records in a paediatric oncology ward of a public acute care hospital in Hong Kong. After explaining the study details, including its purpose, procedures and potential harms and benefits, parents allowing their children to take part are required to sign a consent form. In addition, the children who are going to participate are invited to write down their names on a specially designed child assent form and told that their participation is voluntary.