1. Department of Disease Prevention and Control, No. 960 Hospital of PLA, Jinan, Shandong 250031, P.R. China
2. Electrocardiogram Room, Yantai Yuhuangding Hospital Affiliated to Qingdao University, Yantai, Shandong 264001, P.R. China
3. Department of Training, No. 960 Hospital of PLA, Jinan, Shandong 250031, P.R. China
4. Department of Laboratory Diagnosis, No. 960 Hospital of PLA, Jinan, Shandong 250031, P.R. China