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Article History

Received: 19 September 2018

Accepted: 27 November 2018

First Online: 5 December 2018

Compliance with ethical standards

: Centre of Clinical Documentation and Evaluation (SKDE) holds a concession from the Norwegian Data Protection Authority to access data from the Norwegian Patient Registry (NPR) for patients treated at Norwegian hospitals in the period 1 January 2012 to 31 December 2016. The Norwegian Data Inspectorate licenced the data registry at SKDE (ref.CitationRef removed/00271–2/CGN and 16/00289–2/CGN). Further ethical approval was not required according to Norwegian law.

: Data from the Norwegian Patient Register has been used in this publication. The interpretation and reporting of these data are the sole responsibility of the authors, and no endorsement by the Norwegian Patient Register is intended nor should be inferred.

: The authors declare that they have no conflict of interest.

: This article does not contain any studies with human participants or animals performed by any of the authors.