Footnotes

• Contributors All authors contributed to study conception and design. PN contributed to acquisition of data. PN and MAM contributed to data analysis. All authors contributed to interpretation of data, drafting of manuscript and critical revision. All authors have read and approved the final version of the manuscript and agree with the order of presentation of the authors.

• Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

• Competing interests None declared.

• Patient consent None declared.

• Ethics approval Institutional review board and ethics committee of Tehran University of Medical Sciences.

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