Throughout her career, Elizabeth Selvin, PhD, MPH, has focused on translational projects, providing extensive epidemiological data key to clinical decision-making in diabetes.
For her significant contributions to the field of diabetes epidemiology, Dr. Selvin is the 2020 recipient of the Kelly West Award for Outstanding Achievement in Epidemiology. The award honors the legacy of Kelly M. West, widely regarded as the “father of diabetes epidemiology.”
Dr. Selvin presented her virtual award lecture, The Epidemiology of Hemoglobin A1C—Informing Medical Practice, Sunday afternoon at the Scientific Sessions. Her presentation can be viewed by registered meeting attendees at ADA2020.org through early September.
Dr. Selvin reviewed highlights from decades of epidemiological evidence supporting the use of A1C for the management and diagnosis of diabetes. She also addressed recent controversies and criticism of the biomarker’s limitations.
“There are a number of advantages to A1C as a diagnostic tool for diabetes,” said Dr. Selvin, Professor of Epidemiology and Medicine at Johns Hopkins Bloomberg School of Public Health. “There’s much less biologic variability versus fasting or two-hour glucose. It’s a better index of overall glycemic exposure. It’s well-standardized. It’s relatively unaffected by acute factors. And it’s already used to guide and adjust treatment.”
Dr. Selvin said most criticisms of the use of A1C as a diagnostic test can be answered by clinicians taking note of the particular assay being used, and by viewing results in the context of the individual patient’s overall health. However, the controversary surrounding differences in A1C in black populations compared to white populations surprised her, she said. Higher A1C among black patients led to calls for race-specific cut points when diagnosing diabetes.
Dr. Selvin shared results from a series of studies her group published that look specifically at this issue. She said the racial differences in A1C were small and unlikely to make a difference clinically.
“There’s robust evidence linking A1C with clinical outcomes, and no evidence for racial differences in association with outcomes or in clinical trials of glucose-lowering interventions,” Dr. Selvin said. “The current evidence supports similar interpretation of A1C test results in black and white populations for the diagnosis and treatment of diabetes. Pragmatically, we can use a combination of fasting glucose and A1C to diagnose diabetes while paying attention to any discordance.”
Dr. Selvin also addressed the belief among some clinicians that the profession should “move on” from A1C.
“Some suggest that continuous glucose monitoring (CGM) can overcome the limitations of A1C,” she said. “I think this is a false dichotomy. It’s confusing to say that we should use CGM instead of A1C because A1C is not perfect when CGM is imperfect as well. And they measure different things.”
Dr. Selvin shared data showing the limitations of CGM, and said she believes clinicians should be cautious in thinking the technology can replace A1C.
“We don’t need to choose between a critically important biomarker and a promising new technology,” she said. “We need to remember the importance of epidemiology in informing medical practice. A1C is strongly linked to outcomes and is one of the most important clinical biomarkers in the practice of medicine. Continuous glucose monitoring is a useful tool, but should not replace A1C. Approaches to diagnosis, screening, and management of diabetes should be informed by rigorous epidemiologic studies and sound epidemiologic thinking.”