Erratum

Unfortunately, after publication of this article [1], it was noticed that there was an error in the funding information located in the Acknowledgements section. The full correct Funding section can be seen below.

Acknowledgments

This study is supported by a grant from the Chinese 973 project (No.2012CB517702) and four grants from the National Natural Science Fund (No.81425008, No. 81321064, No. 81370829, and No. 81400724). The authors are very grateful to Prof. Xue-Ying Li for the advice on statistical analysis.

They gratefully acknowledge the contribution of the Department of Clinical Laboratory, Peking University First Hospital.