Received: 1 November 2017
Accepted: 2 August 2018
First Online: 8 August 2018
Ethics approval and consent to participate
: The search in the patient administrative system, compiling of the clinical data and their subsequent statistical analysis were approved by the Data Protection Officer at Oslo University Hospital, with reference to the Norwegian Patient Record Act § 6, cf. the Health Personel Act §26. In short, these acts state that a Norwegian health institution may create internal patient databases for quality control of the treatment, provided that specific guidelines to assure the security of the data are followed. For the creation of such databases patient consent or consent from the Ethical Comitee is not required. The data may be subject to publication if completely anonymized.
: Not applicable.
: The authors declare that they have no competing interests.
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