Published Online: February 4, 2013. doi:10.1001 /jamainternmed.2013.2006
Author Contributions:Study concept and design: King and Chirina. Analysis and interpretation of data: King, Matheson, Chirina, Shankar, and Broman-Fulks. Drafting of the manuscript: King, Matheson, Chirina, and Broman-Fulks. Critical revision of the manuscript for important intellectual content: Chirina and Shankar. Statistical analysis: Chirina. Study supervision: King and Matheson.
Conflict of Interest Disclosures: None reported.
Funding/Support: This study was supported in part by grants 1R01ES021825-01 and 5R03ES018888-02 from the National Institutes of Health.
Additional Contributions: Alexander Brown, MA, assisted in the preparation of the manuscript.