Author Contributions: Dr Tang and Ms Maselli had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Tang, Stein, Gonzales.
Acquisition of data: Hsia, Maselli.
Analysis and interpretation of data: Tang, Stein, Hsia, Maselli, Gonzales.
Drafting of the manuscript: Tang, Stein, Hsia, Maselli, Gonzales.
Critical revision of the manuscript for important intellectual content: Tang, Stein, Hsia, Gonzales.
Statistical analysis: Tang, Stein, Maselli, Gonzales.
Obtained funding: Hsia, Gonzales.
Administrative, technical, or material support: Tang, Hsia.
Financial Disclosures: The primary sponsor of this study was the California HealthCare Foundation grant 08-1256. Additional support was provided by NIH/NCRR/OD UCSF-CTSI grant KL2 RR024130 (J.S., R.Y.H., R.G.), AHRQ grant 1K08HS015569 (J.S.), and the Robert Wood Johnson Foundation Physician Faculty Scholars Program (R.Y.H.).
Role of the Sponsor: The California HealthCare Foundation had no role in the design and conduct of the study; in the collection, analysis, and interpretation of the data; or in the preparation, review, or approval of the manuscript.
Disclaimer: The article contents are solely the responsibility of the authors and do not necessarily represent the official views of the California HealthCare Foundation, National Institutes of Health, Agency for Healthcare Research and Quality, or Robert Wood Johnson Foundation.
Additional Contributions: Eric Vittinghoff, PhD (Division of Biostatistics, Department of Epidemiology and Biostatistics, University of California, San Francisco), provided guidance with the statistical analysis. He did not receive compensation for his contribution.