Author Contributions: Drs Collaco and Cutting 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: Collaco,
Acquisition of data: Collaco, Vanscoy,
Bremer, McDougal, Blackman, Bowers, Naughton, Cutting.
Analysis and interpretation of data:
Collaco, Vanscoy, Bremer, McDougal, Blackman, Bowers, Naughton, Jennings,
Drafting of the manuscript: Collaco,
Critical revision of the manuscript for important intellectual content: Collaco, Vanscoy, Bremer, McDougal, Blackman,
Bowers, Naughton, Jennings, Ellen, Cutting.
Statistical analysis: Collaco, Vanscoy,
Jennings, Ellen, Cutting.
Obtained funding: Collaco, Cutting.
Administrative, technical, or material support:
Bremer, McDougal, Blackman, Bowers, Naughton, Jennings, Ellen, Cutting.
Study supervision: Cutting.
Financial Disclosures: None reported.
Funding/Support: This study is supported by National Heart, Lung, and Blood Institute grant HL68927, Cystic Fibrosis Foundation funding to Drs Collaco and Cutting, and by the Flight Attendant Medical Research Institute.
Role of the Sponsor: The sponsors approved the design and conduct of the study but did not participate in the collection, management, analysis, and interpretation of the data;
or in the preparation, review, or approval of the manuscript.
Additional Contributions: We thank the North American Cystic Fibrosis Foundation for use of the Cystic Fibrosis Foundation Data Registry; Ase Sewall, BS, Monica Brooks,
BS (both of the Cystic Fibrosis Foundation), and the staff at the Data Registry; Nulang Wang, BS, of Johns Hopkins University for CFTR genotyping; Michael Kulich, PhD, of Charles University, Prague, Czech Republic, and Mark Schluchter, PhD, of Case Western Reserve University, Cleveland, Ohio, for providing conversion programs for cystic fibrosis–specific percentiles and Bayes estimates for forced expiratory volume in the first second of expiration,
respectively; John McGready, PhD, of Johns Hopkins University and David Cutler, PhD, of Emory University, Atlanta, Georgia, for helpful statistical discussions; Rita McWilliams, PhD, Julie Hoover-Fong,
MD, PhD, and Ada Hamosh, MD, MPH, all of Johns Hopkins University,
for designing questionnaires; and most importantly the patients with cystic fibrosis and their families, research coordinators, nurses,
and physicians who are participating in the Cystic Fibrosis Twin and Sibling Study. Ms Wang and Dr Cutler received funding through grants.