Author Contributions: Dr Zhao had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Wu, Zhao.
Acquisition of data: Wu, Zhao, Fang,
Analysis and interpretation of data:
Wu, Zhao, Jin, Shao, Guo, Liu, Chen.
Drafting of the manuscript: Wu, Zhao.
Critical revision of the manuscript for important intellectual content: Wu, Zhao, Jin, Shao, Fang, Guo, He, Liu,
Statistical analysis: Wu, Zhao.
Obtained funding: Zhao.
Administrative, technical, or material support:
Wu, Shao, He, Chen, Li.
Study supervision: Wu, Zhao.
Financial Disclosures: None reported.
Funding/Support: The research was supported by National Key Technologies R&D Program in the 10th 5-year-plan grant 2004BA720A22 from the Ministry of Science and Technology of the People's Republic of China.
Role of the Sponsor: The funding organizations played no role in the design, conduct, analysis, or interpretation of the research or in any aspect of preparation or approval of the manuscript.