PURPOSE The health care system in the United States is inherently hierarchical. Patients
are “nested” within physicians who in turn are “nested” within practices. Much of the …

Results of medical research studies are often contradictory or cannot be reproduced. One
reason is that there may not be enough patient subjects available for observation for a long …

Recent advances in statistical software1 have enabled public health researchers to fit
multilevel models to a variety of outcome variables. Multilevel models facilitate inferences …

Studies in which data from multiple patients are collected per clinician or per practice are
becoming common in primary care research, particularly with the increase of studies …

Practice-based research networks (PBRNs) have emerged as laboratories in which to
address important primary care challenges. In 2011, the Agency for Healthcare Research …

Multilevel data occur frequently in health services, population and public health, and
epidemiologic research. In such research, binary outcomes are common. Multilevel logistic …

Research conducted in a practice-based research network (PBRN) differs from other
multisite research and presents particular planning challenges. The American Academy of …

Background Centralized and federated models for sharing data in research networks
currently exist. To build multivariate data analysis for centralized networks, transfer of patient …

Although well-designed randomized controlled trials (RCT) provide the strongest evidence
regarding causation, only relatively recently have they been used by health services …

Ten years have passed since we wrote “A Short History of Primary Care Practice-based
Research Networks: From Concept to Essential Research Laboratories.” 1 In that essay we …