Received: 21 December 2017
Accepted: 2 May 2018
First Online: 11 May 2018
Ethics approval and consent to participate
: In this study only previously collected data was used and the data analysed was de-identified. The project was registered with the Homerton University Hospital (registration number 2377/2818) prior to the commencement of the study, who waived the need for ethics approval.
: The authors declare that they have no competing interests.
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