Received: 17 September 2017
Accepted: 28 February 2018
First Online: 7 March 2018
Ethics approval and consent to participate
: The ethics approval was obtained from SingHealth Centralised Institutional Research Board (CIRB Ref: 2016/2780). The need for consent was formally waived by the ethics committee in CIRB.
: Not applicable.
: The authors declare that they have no competing interests.
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