Received: 5 April 2017
Accepted: 24 January 2018
First Online: 30 January 2018
Ethics approval and consent to participate
: Ethical approval was obtained from Institutional Review Board of the University of Hong Kong/Hospital Authority Hong Kong West Cluster (HKU/HA HKW IRB, Reference number: UW 14–200). Informed written consent were obtained from all participants.
: Not applicable.
: The authors declare that they have no competing interests.
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