Conflict of interest

On behalf of all authors, the corresponding author states that there are no conflicts of interest.

Ethical approval

The study was approved by the Peking University First Hospital Clinical Research Ethics Committee 2013[548]. This was a retrospective study. All patients in the study were from our prospective cohort in which all patients signed the consent form when they were recruited into the cohort.

Consent to participate

Patient consent has been obtained to participate.

Consent for publication

Patient consent has been obtained for publication.