1. Department of Geriatrics, the Second Xiangya Hospital, Central South University, Changsha, Hunan, China
2. Department of Clinical Laboratory, Xiangya Hospital of Central South University, Changsha, Hunan, China
3. Department of Clinical Medicine, Xiangya Medical School of Central South University, Changsha, Hunan, China
4. Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA