The Johns Hopkins ACG® System grew out of clinical observations made by Barbara Starfield, MD, MPH, in pediatric populations. Research by Dr. Starfield and her colleagues in the early 1980s showed that children using the most health care resources were not those with a single chronic illness, but rather children with multiple, seemingly unrelated conditions. Dr. Starfield was able to extend these findings to all patients and ultimately demonstrate that the clustering of morbidity is a better predictor of health services resource use than the presence of specific diseases. Clustering of morbidity forms the basis of the current ACG System and remains the fundamental concept that differentiates ACGs from other case-mix adjustment methodologies.
Today the ACG System offers a suite of health-based risk adjustment approaches that are used by healthcare providers, health plans, and public-sector agencies. The ACG System has a uniquely clinical perspective on person health that emphasizes the inter-relationship of multiple diseases to explain healthcare utilization both retrospectively and prospectively. The ACG System has withstood the financial and clinical pressures of the healthcare marketplace to become a statistically valid and industry standard risk adjustment and predictive modeling methodology.