Received: 7 November 2020
Accepted: 20 April 2021
First Online: 28 April 2021
: The Ethics Committee of the Fourth People’s Hospital of Chengdu has approved of this research. We have obtained informed consent from all subjects, which would tell all callers that their all information is recorded anonymously, and their data would be analyzed if they agreed. Subjects under the age of 18 also were obtained informed consent from their legally authorized guardians. All methods were performed in accordance with the relevant guidelines and regulations of WMA declaration of Helsinki - ethical principles for medical research involving human subjects.
: Not applicable.
: The authors declare that they have no competing interests.