Received: 8 May 2017
Accepted: 29 January 2018
First Online: 7 February 2018
Ethics approval and consent to participate
: The study protocol was approved by the institutional review boards (IRB) at ethics committee of Tehran University of medical sciences (IR.TUMS.VCR.REC.1396.2314).
: Not applicable.
: The authors declare that they have no competing interests.
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