previous research has demonstrated varying degrees of accuracy in pneumonia coding by hospitals [27,28]. We developed an administrative claims-based model for profiling hospitals for pneumonia mortality that is a good proxy for results from a medical record model. Despite limitations of currently available data, this model represents a valuable tool in assessing the outcomes achieved by states and hospitals in caring for patients with pneumonia, and has been endorsed by the National Quality Forum as a measure for acute care hospital performance [29]. Since initial development, several minor changes have been made to the model including expanding the cohort to include patients with viral pneumonia (adenovirus [480.0], respiratory syncytial virus [480.1], and parainfluenza virus [480.2]), and excluding patients who had enrolled in the Medicare hospice benefit before hospitalization (,1% of patients with pneumonia) [30]. CMS first began using the model for public reporting in August 2008 and hospital-specific findings are now reported on Hospital Compare [31]. Supporting Information Table S1 Pneumonia study sample used for the derivation and validation cohorts. (DOC) References 1. Russo CA, Elixhauser A (2006) Hospitalizations in the elderly population, 2003. Statistical Brief #6. Rockville: Agency for Healthcare Research and Quality, Available: http://www.hcup-us.ahrq.gov/reports/statbriefs/sb6.pdf. Accessed 2011 Mar 22. 2. Fry AM, Shay DK, Holman RC, Curns AT, Anderson LJ (2005) Trends in hospitalizations for pneumonia among persons aged 65 years or older in the United States, 1988–2002. JAMA 294: 2712–2719. 3. Anderson RN, Smith BL (2005) Deaths: leading causes for 2002. National Vital Statistics Reports; vol 53 no 17. Hyattsville: National Center for Health Statistics, Available: http://www.cdc.gov/nchs/data/nvsr/nvsr53/nvsr53_17. pdf. Accessed 2011 Mar 22. 4. 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Accessed 2011 Mar 22. PLoS ONE | www.plosone.org 7 April 2011 | Volume 6 | Issue 4 | e17401