Author Contributions: Dr van der Windt 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: van der Windt, Jellema, Mulder, Kneepkens, van der Horst.
Acquisition of data: van der Windt, Jellema, Kneepkens.
Analysis and interpretation of data: van der Windt, Jellema, Kneepkens.
Drafting of the manuscript: van der Windt.
Critical revision of the manuscript for important intellectual content: Jellema, Mulder, Kneepkens, van der Horst.
Statistical analysis: van der Windt.
Obtained funding: van der Windt, Mulder, van der Horst.
Administrative, technical, or material support: Jellema.
Study supervision: van der Windt, van der Horst.
Financial Disclosures: None reported.
Funding/Support: This study was supported by grant 945-06-001 from the Netherlands Organization for Health Research and Development, the Hague, the Netherlands.
Role of the Sponsor: The funding organization played no role in the design and conduct of the review; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript.