Received: 19 December 2017
Accepted: 4 February 2018
First Online: 14 February 2018
Ethics approval and consent to participate
: For this study, formal consent is not required. This was approved by the institutional Medical Research Ethics Committee, protocol number VUmc 2011/199, and in accordance with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
: Not applicable.
: The authors declare that they have no competing interests.
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