The Affordable Care Act and other federal policy initiatives have created incentives for smaller practices to consolidate into larger medical groups or be acquired by hospitals. It is often assumed that larger practices provide better care. However, a new study, recently released as a Web First by Health Affairs, showed unexpected results: Practices with 1-2 physicians had 33 percent fewer preventable hospital admissions than practices with 10-19 physicians.

This study, which used data from the National Study of Small and Medium-Sized Physician Practices (NSSMPP) and surveyed 1,745 physician practices between July 2007 and March 2009, is believed to be the first of its kind in the United States. The study sample was limited to practices where at least 60 percent of the physicians were primary care providers, cardiologists, endocrinologists, and pulmonologists.

Authors Lawrence Casalino, Michael Pesko, Andrew Ryan, Jayme Mendelsohn, Kennon Copeland, Patricia Pamela Ramsay, Xuming Sun, Diane Rittenhouse, and Stephen Shortell identified physician specialties through the use of Medicare claims. “These findings were unexpected, since small practices have fewer resources,” observed the authors. “But it is possible that small practices have characteristics that are not easily measured but result in important outcomes.”

They recommend that hospitals and medical groups absorbing physician practices consider “whether there are advantages to trying to preserve the small practice environment within their organizations, while providing resources to help small practices proactively improve care for their populations of patients.”

Casalino, Pesko, and Ryan are affiliated with Weill-Cornell Medical College in New York; Mendelsohn is a postbaccalaureate premedical student at Bryn Mawr College in Pennsylvania; Copeland is with NORC at the University of Chicago in Illinois; Ramsay and Shortell are affiliated with the University of California, Berkeley; Sun is employed by the New York City Department of Health and Mental Hygiene; and Rittenhouse is with the University of California, San Francisco.

This study, which was supported by The Commonwealth Fund and the Robert Wood Johnson Foundation, will also appear in the September issue of Health Affairs.