Author Contributions: Dr Liu 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: Liu. Acquisition of data: Liu and Cheung. Analysis and interpretation of data: Liu, Cheung, and Bravata. Drafting of the manuscript: Liu, Cheung, and Bravata. Critical revision of the manuscript for important intellectual content: Liu and Bravata. Statistical analysis: Liu and Bravata. Administrative, technical, and material support: Liu and Cheung. Study supervision: Liu.