Footnotes

• Competing interests None declared.

• Patient consent Obtained from the parents/guardian.

• Ethics approval Ethics Committee of Federal University of Paraná.

• Provenance and peer review Not commissioned; internally peer reviewed.

• Correction notice This paper has been amended since it was published Online First. Owing to a scripting error, some of the publisher names in the references were replaced with ’BMJ Publishing Group'. This only affected the full text version, not the PDF. We have since corrected these errors and the correct publishers have been inserted into the references.