Background: Healthcare quality measurement in the United States has evolved from isolated chart audits into a data-intensive discipline spanning capture, risk adjustment, statistical monitoring, and structured improvement, anchored by the Institute of Medicine’s six aims for a high-quality health system.

Objective: To provide a detailed, data-oriented narrative review of the principal data sources, national measurement frameworks, and quality-improvement methodologies used in U.S. hospitals and health plans, combining current national performance statistics with clearly labeled worked examples of measure specification, risk adjustment, and statistical process control.

Methods: This is a narrative (non-systematic) review. Publicly available technical documentation, methodology reports, national performance data, and policy materials from the National Committee for Quality Assurance (NCQA), the Centers for Medicare & Medicaid Services (CMS), the Agency for Healthcare Research and Quality (AHRQ), The Leapfrog Group, the Kaiser Family Foundation (KFF), and the Institute for Healthcare Improvement (IHI) were consulted, supplemented by peer-reviewed and health-policy literature identified through targeted search.

Results: Five commonly used national measurement systems HEDIS, the CMS Overall Hospital Quality Star Ratings, HCAHPS, AHRQ Patient Safety Indicators, and the Leapfrog Hospital Safety Grade account for most publicly reported hospital and health-plan quality data in the United States. In the April 2026 Star Ratings refresh, 3,203 of roughly 4,600 eligible hospitals received a rating, with 12.0% earning 5 stars and 6.4% earning 1 star. The Hospital Readmissions Reduction Program (HRRP) has penalized a majority of assessed hospitals in most years since fiscal year 2013, with the average payment reduction across assessed hospitals ranging from roughly 0.3% to 0.6% depending on the year, alongside a documented decline in the national Medicare 30-day all-cause readmission rate from an average of 19.0% (2007–2011) to 18.5% in 2012 and further thereafter. Standardization methods such as z-score normalization, used operationally by the Leapfrog Hospital Safety Grade, and structured improvement methods Plan-Do-Study-Act (PDSA) cycles, Lean, Six Sigma, and high-reliability organizing translate measurement into performance gains. Persistent disparities across demographic and socioeconomic subgroups remain evident even as aggregate performance improves, motivating an expanding CMS health-equity measurement agenda. Conclusion: Reliable data capture, faithful application of standardized national measure specifications, disciplined use of improvement methodology, and continued attention to health equity together form the pipeline through which U.S. healthcare quality measurement translates into better patient outcomes.

Keywords: healthcare quality measurement, HEDIS, CMS Star Ratings, patient safety indicators, Plan-Do-Study-Act, risk adjustment, health equity, United States.