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Become a member and receive career-enhancing benefits

Our top priority is providing value to members. Your Member Services team is here to ensure you maximize your ACS member benefits, participate in College activities, and engage with your ACS colleagues. It's all here.

Become a Member
Become a member and receive career-enhancing benefits

Our top priority is providing value to members. Your Member Services team is here to ensure you maximize your ACS member benefits, participate in College activities, and engage with your ACS colleagues. It's all here.

Membership Benefits
About Quality Programs

ACS Clinical Scholar in Residence Mentors

Mark E. Cohen, PhD

Statistical Manager, Continuous Quality Improvement, Division of Research and Optimal Patient Care, American College of Surgeons, Chicago, IL

Dr. Cohen received a PhD in psychology from the University of Illinois, Chicago, and also completed graduate-level coursework in applied statistics at DePaul University, Chicago. Dr. Cohen was a National Institutes of Health postdoctoral fellow at the University of Wisconsin, Madison, and taught at Lake Forest College, Lake Forest, IL. Before coming to the College in 2008, he worked at a U.S. Navy Medical Research Laboratory for 28 years as a statistician and as technical (research) director. Dr. Cohen has authored 165 peer-reviewed articles. He manages the CQI statistics team which is responsible for profiling analytics for the ACS National Surgical Quality Improvement Program (ACS NSQIP), Pediatric NSQIP, and the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP), as well as other quantitative efforts involving ACS staff, consultants, and clinical scholars.

Bruce L. Hall, MD, PhD, MBA, FACS

Dr. Hall received his MD and PhD from the NIH Medical Scientist Training Program at Duke University, Durham, NC, and later obtained an MBA from Harvard Business School, Boston, MA. Dr. Hall holds dual appointments as associate professor in the department of surgery at Washington University/Barnes-Jewish Hospital and the Olin Business School, St. Louis, MO. His clinical expertise includes thyroid and parathyroid surgery, surgical oncology, and trauma care. He joined the John Cochran Saint Louis VA Medical Center Surgical Service as the associate chief of surgery in 2007. He is also a senior fellow of the Center for Health Policy at Washington University.

Dr. Hall has focused his research on the evaluation of quality in surgery. He has particular interest in the theory of risk adjustment and advanced statistical techniques. He has directed the ACS NSQIP at his hospital since 2001. Nationally, Dr. Hall co-chairs the Measurement and Evaluation Committee for the ACS NSQIP, serves on the ACS NSQIP Policy Advisory Committee and the ACS Patient Safety and Quality Committee, represents the ACS to the National Quality Forum, and is a member of the physician engagement group for The Joint Commission. Dr. Hall has mentored a large number of students and residents conducting health outcomes research.

Clifford Ko, MD, MS, MSHS, FACS

Director, Division of Research and Optimal Patient Care, American College of Surgeons (ACS), Chicago, IL

Dr. Ko is the Director of the Division of Research and Optimal Patient Care at the American College of Surgeons (ACS) where he oversees all the quality improvement and accreditation/verification programs and activities of the division, including those related to bariatric, cancer, pediatric, and trauma surgeries. He also oversees the Surgeon Specific Registry (SSR), the Coalition for Quality in Geriatric Surgery (CQGS), and the Improving Surgical Care and Recovery (ISCR) project informed for enhanced recovery protocols. Dr. Ko also serves as the Director of the ACS National Surgical Quality Improvement Program (ACS NSQIP), and professor of surgery at the University of California, Los Angeles. He is a double board-certified surgeon, specializing in general and colorectal surgery, and a formally trained health services researcher. Prior to working at the ACS, he served as a research scientist at the RAND Corporation. Dr. Ko has published nearly 400 peer-reviewed articles, written more than 20 book chapters, and received peer-reviewed funding from several sources including the National Institutes of Health and the Agency for Healthcare Research and Quality. He has extensive experience in guiding residents and fellows conducting research on health outcomes.

Ryan P. Merkow, MD, MS

Dr. Merkow is a board-certified surgical oncologist focusing on upper gastrointestinal malignancies, and is a health services researcher at Northwestern University. He received his formal training in health services research at the American College of Surgeons as a Clinical Scholar in Residence and completed a Master’s in Health Services and Outcomes Research in the Center for Healthcare Studies at Northwestern University. He is currently on faculty in the Surgical Outcomes and Quality Improvement Center (SOQIC) at Northwestern University and a Faculty Scholar at the American College of Surgeons. Dr. Merkow’s research focus includes perioperative surgical quality, cancer care quality measure development, and patient-reported outcomes. Dr. Merkow has published more than 65 scientific articles in journals such as JAMA, JNCI, and Annals of Surgery. He has extensive experience mentoring students and residents in the field of health services research.

Avery Nathens, MD, MPH, PhD

Dr. Nathens is the Medical Director of Trauma Quality Programs at the American College of Surgeons, Professor of Surgery at the University of Toronto and a practicing trauma surgeon and the medical director of trauma at Canada’s largest trauma center. He completed his trauma and critical care fellowship at Harborview Medical Center at the University of Washington and joined the faculty there in 2000 as Director of Surgical Critical Care and the Director, Acute Care Section of the CDC - funded Harborview Injury Prevention and Research Center. As Medical Director of Trauma Quality Programs at the ACS, he oversees the Trauma Center Verification and Review Program and the  Trauma Quality Improvement Program (TQIP), where centers receive benchmarking reports allowing them to compare their performance to their peers. 

Dr. Nathens holds a PhD from the University of Toronto, a Masters in Public Health from the University of Washington, and has cross appointments at the Institute of Clinical Evaluative Sciences (IC/ES) and the Institute of Health Policy, Management, and Evaluation at the University of Toronto. He holds the DeSouza Chair in Trauma Research and has published over 450 manuscripts including many landmark peer-reviewed papers in the Lancet, NEJM, and JAMA. He has been awarded several million dollars in funding from the NIH, CDC, and other agencies for his research evaluating trauma care.

Heidi Nelson, MD, FACS

Dr. Nelson is the Medical Director of Cancer Programs for the American College of SurgeonsShe is emeritus Chair of the Department of Surgery and past Chair of the Division of Colon & Rectal Surgery at Mayo Clinic in Rochester. Dr. Nelson is an emeritus member of the Mayo Clinic Board of Trustees and Mayo Clinic Board of Governors. She is the former Director of the Microbiome Program through Mayo Clinic’s Center for Individualized Medicine.

Dr. Nelson’s career focused on advancing the care of patients with colorectal cancer through the advancement of new technologies, standardization and biologic studies. Her international research trial on laparoscopic colectomy versus open colectomy surgery for colon cancer re-defined best surgical practice in the approach to surgery for colon and rectal cancer patients. Dr. Nelson was PI of the NIH-funded COST Laparoscopic Trial and served as group co-Chair of the American College of Surgeons Oncology Group. She is past President of the American Society of Colon and Rectal Surgeons Research Foundation, past Chair of two NIH study sections and served as a member of the NCI Clinical Trials Advisory Committee.