Conflicting interests 
The authors declare that there is no conflict of interest.Funding 
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.Informed consent
Informed consent was not sought for the present study because it was an analysis of routine clinical data.Ethical approval
Ethical approval was not sought for the present study because it did not directly involve human participants. This study was completed in accordance with the Helsinki Declaration as revised in 2013.