1. National Center for Clinical Laboratories, Beijing Hospital, National Center of Gerontology, Beijing 100730, P. R. China
2. Graduate School, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing 100730, P. R. China
3. Beijing Engineering Research Center of Laboratory Medicine, Beijing Hospital, Beijing 100730, P. R. China
4. Division of Pathology & Laboratory Medicine, Hebei Yanda Lu Daopei Hospital, Langfang 065201, P. R. China