Johns Hopkins ACG System
Population Health Analytics

Our team of population health experts apply the most advanced tools to analyze your data and provide insights you need. We then recommend interventions to improve your population’s health and impact your health care costs.


About the ACG System:  Population Health Analytics

The ACG System explains and predicts how health care resources are delivered and consumed. It identifies persons who are likely to become high-resource users or to become hospitalized, provides important clinical context to aid in managing patient care, and makes available customized models unique to each organization.


The Johns Hopkins Advantage

For 130 years, Johns Hopkins Hospital has led the way in both biomedical discovery and health care, establishing the standard by which others follow and build upon. This is one of many faculty-developed programs, protocols and services provided by Johns Hopkins HealthCare Solutions to improve health outcomes and reduce the cost of care. Our faculty experts developed this program for maximum impact, based on years of research and clinical success.


Common Applications for the ACG System

Health care costs are rising. To change that trend you need to analyze and understand the health and care of your population. Our team of population health experts apply the most advanced tools to analyze your data, including:

  • Identify prevalent diseases and cost drivers
  • Predict hospitalization risk
  • Evaluate provider performance
  • Adjust capitation rates

We then recommend interventions to improve your population’s health and impact your health care costs.  For more information, visit

Population Health Analytics





About the ACG System

The distinguishing feature of the ACG System is its “person-focused” approach, which allows it to capture the multidimensional nature of an individual’s health over time. Also, the ACG System is able to handle, describe and manage healthier populations (i.e., low users of healthcare services). Unlike other similar systems, the ACG system was developed using commercial managed care populations as well as state Medicaid populations, both of which closely resemble the general population. And the Johns Hopkins ACG System—which has been updated to reflect user suggestions and to respond to user needs—has been used in commercial and research settings worldwide, longer and more extensively than any other system currently available.

Among its unique strengths are

  • its focus on categorizing people, not diagnosis codes;
  • its ability to support the full spectrum of management applications;
  • its refusal to base complexity on specific procedures or hospitalizations;
  • its capacity to provide more than a simple score;
  • its foundation built upon a well-defined set of clinical indicators that have been vetted in the health services research literature;
  • its maximal use of available data selected from a suite of predictive models;
  • its flexibility and ability to be customized.

For more information, visit



The Johns Hopkins Advantage

Jonathan Weiner is a co-developer of the Johns Hopkins ACG System. He is a professor of health policy and management at the Johns Hopkins Bloomberg School of Public Health. He is also a professor of health informatics at the Johns Hopkins School of Medicine’s division of health sciences informatics. His current research focuses on the application of electronic health records (EHRs) and HIT for population based applications such as performance measurement and predictive modeling/analytics.

Professor Weiner is the director of the newly formed Johns Hopkins Center for Population Health Information Technology (CPHIT) which focuses on R&D related to the application of EHRs, e-health and other HIT to the health of populations, integrated delivery systems and public health agencies. On the training side, he is the director of the Johns Hopkins doctoral training program in health services research & policy. He is also the director of the Johns Hopkins public health informatics certificate training program. He is an internationally regarded researcher, policy analyst and lecturer. His expertise includes: managed care and integrated health care delivery systems; predictive modeling, risk adjustment and healthcare analytics; healthcare IT and health system integration; quality of care measurement, health workforce deployment & planning, and cross-national comparisons in the primary care sector. He is the author or co-author of over 130 peer reviewed articles. He is a frequent consultant to integrated delivery systems and managed care organizations around the nation and globe.

Professor Weiner holds a doctorate of public health (Dr.P.H.) in health services research from the Bloomberg School of Public Health. He also holds an M.S. in health administration from the University of Massachusetts and a B.A. in human biology from the University of Pennsylvania.

Chad Abrams has been a member of the ACG System team since 1994. Today he utilizes his extensive experience with the ACG System as well as his knowledge of the Affordable Care Act, to apply the ACG System to the new health care delivery landscape in the United States. He also works directly with a variety of North American and governmental agencies and academic users to help bridge the gap between academic research and application of risk adjustment in real world settings. Mr. Abrams also has broad programming experience with SAS, AUTOGRP, and PC-Group software, and he is an author of several academic articles concerning the application of the ACG System. Mr. Abrams earned a master’s degree in economics from the University of California, Davis and a bachelor’s degree in economics from the College of William and Mary.

Dr. Steve Sutch has been working with the ACG System Team since 2007. He has over 20 years experience of working in the National Health Service (NHS) in Great Britain at local, regional and national levels. He has worked with data and data collections from various aspects of activity and financial returns. His lead role in the design of HRGv35, a tool currently used for hospital payments in NHS England– and its updated version HRGv4– led to the development of analytical methods on routinely collected NHS data as well as other clinical data collections. He has an extensive working and practical knowledge of the HES/NWCS/SUS data collections.

He also worked on benchmarking systems for commissioning in Great Britain to develop a national system of tools, first in NHS Wales and later in England. As the Analytical and Statistical Services Manager of the NHS Information Authority National, Dr. Sutch oversaw the continued development of national benchmarking products, and supported the initial development of the program budget categories. He also sat on the committees responsible for the implementation of ICD-10 codes in England and Wales, and then led the development of HRGs that formed a major contribution to the redevelopment of the surgical classification (OPCS4.3, 4.4).

Through the Kings Fund project, and subsequent projects with various PCTs, Dr. Sutch has gained expertise in the application of ACGs® to NHS ambulatory data.

Dr. David Bodycombe is responsible for formulating and overseeing the R&D agenda of the lab. He is actively engaged in all phases of moving the work of the lab from initial conceptualization, methodological design, and analytics, to deployment and publication. He has more than 40 years of experience in statistics, the design and construction of large clinical and epidemiologic databases, statistical programming, and information technology applications development.

Prior to joining the Johns Hopkins Bloomberg School of Public Health faculty, Dr. Bodycombe served as Vice President of Analytics for Premier Inc., a major quality improvement and supply chain management organization. In addition, he was Director of Research for the American College of Cardiology. He has also consulted on a wide range of projects concerning prison healthcare, Native American sanitation programs, and HIV in minority communities.

Dr. Bodycombe holds a ScD in Health Policy and Management and a Baccalaureate degree in Biology from the Johns Hopkins University, as well as an MSc in Biostatistics from Georgetown University.

Thomas Richards has been with the ACG System Team since 1989. An electrical engineer by training, Mr. Richards designed and programmed all command line versions of the ACG System software, including Windows, all UNIX variants, and the assembly language MVS version. Mr. Richards provides technical support to the ACG System Team on the development of data bases used for further research and development of the ACG System products. Mr. Richards also created SKYTALE, HIPAA compliant software for encrypting/de-encrypting patient identifiers on claim level data. He was the chief technical architect for the Sentinel Centers Network database and has spoken at conferences on the use of ACGs with data from federally funded community health centers.

Mr. Richards holds a MSEE in Electrical Engineering and a BEE in Engineering from the Johns Hopkins University, as well as a BS in Applied Mathematics from the George Washington University.

Dr. Lemke has been a member of the ACG System’s Team since 1998. A statistician by training, his primary expertise is in the development, management and analysis of health services data with an emphasis on applying risk-adjustment methodologies. Dr. Lemke is a SAS Certified Professional with extensive experience in the analysis of large administrative databases. His prior experience includes work as a Research Statistician for the Maryland Health Care Commission. Dr. Lemke is also the primary contact for all ACG System projects in Germany and has ensured the successful on-going use of the ACG System there.

Dr. Lemke received a Ph.D. degree in Statistics and Industrial Engineering with a concentration in Operations Research from Iowa State University in 1992. He also holds an M.Sc. degree in Statistics from the University of Georgia. Dr. Lemke has co-authored several research articles that required in-depth knowledge of the ACG System.

Dr. Chang joined the ACG System team in 2003. He applied the ACG System in Taiwan’s National Health Insurance scheme showing that the ACG System could be adopted in Asian countries, despite the different health care systems from those in western countries. He has also participated in the incorporation of the longitudinal element into the ACG system, including morbidity trajectory and consistent high-cost users. He continues to work on multiple ACG System development projects including incorporating electronic medical records, developing opioid abuse markers, and refining frailty indicators.

Dr. Chang received his Doctor of Philosophy degree in 2009 from the Johns Hopkins Bloomberg School of Public Health under the supervision of one of the founders of the ACG System: Dr. Jonathan Weiner; while at the same time obtained a Masters degree in Biostatistics at Johns Hopkins. Prior to joining the Johns Hopkins University, he received a Master degree of Health Policy and Management from Harvard University.

Originally from Taiwan, Dr. Chang obtained his Bachelor degree of Public Health from the National Taiwan University in 1995, and then completed his first Master degree of Health and Welfare Policy at the National Yang-Ming University in 1997.