1. Center for Healthcare Quality and Outcomes, Research Triangle Institute , Research Triangle Park, North Carolina, USA
2. Merck & Co., Inc. , Rahway, New Jersey , USA
3. Research Triangle Institute , Waltham, Massachusetts , USA
4. Westat Insight, Boston , Massachusetts , USA
5. US Department of Health and Human Services, Office of the Assistant Secretary for Planning and Evaluation , Washington, District of Columbia , USA