Author Contributions: Dr Go 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: Go, Lee, Yang, Gurwitz.
Acquisition of data: Go, Yang.
Analysis and interpretation of data: Go, Yang, Lo, Gurwitz.
Drafting of the manuscript: Go, Lee.
Critical revision of the manuscript for important intellectual content: Go, Lee, Yang, Lo, Gurwitz.
Statistical analysis: Go, Yang.
Obtained funding: Go.
Administrative, technical, or material support: Go.
Study supervision: Go.
Financial Disclosures: Dr Go and Ms Yang reported receiving research support for this study from Amgen Inc. Dr Go also reported receiving research support from Wyeth. Dr Lo reported receiving research support from Novartis. None of the other authors reported disclosures.
Funding/Support: The research for this article was funded by a grant from Amgen Inc.
Role of the Sponsor: Amgen Inc had no role in the design, collection, analysis, and interpretation of data; in the writing of the manuscript; or in the preparation or decision to submit the manuscript for publication.
Independent Statistical Analysis: All analyses were performed by Jingrong Yang, MA, a biostatistician and SAS analyst who works exclusively for the Kaiser Division of Research. She received statistical consultation from Lynn Ackerson, PhD, who also works exclusively for Kaiser's Division of Research.
Acknowledgment: We thank Lynn M. Ackerson, PhD, for her statistical input and Krista L. Lepper, BA, for her expert technical assistance. Both Dr Ackerson and Ms Lepper received research support from Amgen Inc for their work.