Massive National Review of 1.4 Million Surgeon Trainee Cases Reveals How Residents Learn Safety Through Quality Data

In one of the largest examinations of surgical training outcomes ever assembled, researchers affiliated with the American College of Surgeons have analyzed more than 1.4 million operative cases linked to individual surgical residents across the United States, offering the most comprehensive picture to date of how trainee involvement relates to patient outcomes and how a national data infrastructure can double as an educational platform. The study, published in Global Surgical Education, the Journal of the Association for Surgical Education, centers on the Quality In-Training Initiative, or QITI, a program developed by the American College of Surgeons to connect resident participation in surgery with the rich clinical outcomes data collected through the ACS National Surgical Quality Improvement Program, widely known as NSQIP.

The premise behind QITI is deceptively simple but technically demanding. NSQIP has long served as one of the most rigorous surgical outcomes registries in the world, capturing standardized preoperative risk factors, operative details, and thirty-day postoperative outcomes across hundreds of hospitals. What NSQIP traditionally did not do, however, was tie those outcomes to the specific trainees who participated in each operation. QITI was created to close that gap, adding structured fields that identify the postgraduate year level of the resident involved in each case. By linking trainee identity and experience level to meticulously audited outcomes, the initiative aims to transform a hospital quality program into a living laboratory for surgical education, giving residents and program directors access to the same kind of risk-adjusted performance data that practicing surgeons encounter in their professional lives.

The new analysis is a retrospective study of NSQIP cases with completed QITI fields spanning July 2013 through July 2025. The scale is striking: 190 participating institutions contributed cases, and 1,412,068 met the study’s inclusion criteria, of which 1,098,264 involved residents in the postgraduate years one through five, the core of general surgery training. The research team, led by Caroline O. Smolkin of the American College of Surgeons’ Division of Research and Optimal Patient Care, together with colleagues from institutions including Northwell Health, the University at Buffalo, Zucker School of Medicine, Vanderbilt, the University of Pennsylvania, and UCLA, conducted descriptive analyses of case volume, institutional participation, operative case mix, and postoperative outcomes stratified by postgraduate year. They then applied multivariable regression models to assess the association between trainee seniority and outcomes after adjusting for the standard NSQIP preoperative risk factors that account for differences in patient sickness at the time of surgery.

One of the clearest findings concerns the changing texture of the operative experience as residents progress. The case mix increased in complexity across postgraduate year levels, a pattern consistent with the graduated responsibility that training programs are designed to provide. Junior residents predominantly logged procedures that form the foundation of technical surgical competence, while senior residents participated in longer, more physiologically demanding operations. Yet the data also revealed continuity: certain index procedures, notably laparoscopic appendectomy and laparoscopic cholecystectomy, remained common at every training level. These operations, among the most frequently performed emergency general surgery procedures in the country, appear to function as a throughline of residency, providing recurring opportunities for deliberate practice from the first year through the fifth, with each repetition layered onto progressively deeper mastery.

The outcomes analysis produced a finding that at first glance might alarm patients: unadjusted complication rates increased stepwise with postgraduate year level, a statistically robust trend across the cohort. The apparent interpretation, that more senior residents are associated with worse outcomes, would be profoundly misleading, and the study’s technical design was built precisely to expose why. Senior residents are assigned to longer and more complex cases on sicker patients, and those operations carry higher baseline risk regardless of who stands at the table. Raw, unadjusted comparisons conflate the characteristics of the case with the characteristics of the trainee, which is why risk adjustment is the essential analytic lens for any investigation of resident involvement in surgery.

After the researchers adjusted for standard preoperative risk factors, most of the differences in complication rates across training levels attenuated, indicating that much of the raw disparity reflects case selection rather than trainee performance. However, the adjustment did not erase every signal. Cases involving fifth-year residents remained significantly associated with higher odds of select outcomes, including intubation, prolonged ventilation, renal complications, cardiac complications, readmission, overall morbidity, and mortality. This residual association most plausibly reflects the fact that chief residents participate in the highest-acuity operations in the hospital, where prolonged operative times and complex physiology drive complications independent of the individual performing the procedure. Prior research has linked prolonged operative duration to increased complications, and chief-resident cases are disproportionately represented among such lengthy, high-complexity operations. A sensitivity analysis restricted to the years 2022 through 2024 showed fewer significant associations, suggesting that these patterns are not immutable features of training but may shift with case mix, supervision practices, and evolving educational structures.

Beyond the epidemiology, the study carries a pointed argument about the purpose of outcome data in education. Surgical training in the United States is steadily shifting toward competency-based frameworks, in which progression is justified by demonstrated ability rather than time served, and toward outcomes-informed models in which real clinical data inform assessment. Milestones developed by the Accreditation Council for Graduate Medical Education and recommendations from national bodies such as the Blue Ribbon II Committee have emphasized the need for meaningful, data-grounded evaluation. QITI offers a substrate for that ambition at a scale no single program could match. Because the registry standardizes definitions of complications, captures thirty-day outcomes through trained reviewers, and applies validated risk-adjustment methodology, the comparisons it generates reflect the same statistical machinery that hospital quality departments and national benchmarking reports use, giving residents authentic exposure to the data environment of modern surgical practice.

The authors frame this as an opportunity to prepare trainees for the quality reports they will encounter as independent surgeons. Practicing surgeons today receive surgeon-specific outcome profiles, participate in departmental quality reviews, and are increasingly held to public and payer-driven performance metrics. A resident who has learned to interpret odds ratios, understand what risk adjustment does and does not capture, and contextualize benchmarked complication rates enters practice with a form of literacy that traditional apprenticeship never provided. Previous studies built on QITI data have explored whether chief resident autonomy is safe for patients and have tracked individual residents’ outcomes over time, and NSQIP-based quality improvement curricula have shown that residents can engage productively with registry data as an educational exercise. The new national review demonstrates that the underlying infrastructure is feasible and sustainable at scale, sustained across more than a decade and nearly two hundred institutions.

The findings also contribute to a long-running debate about patient safety and trainee involvement. Numerous studies across specialties have examined whether resident participation harms outcomes, with results varying by procedure, specialty, and analytic method. What distinguishes the QITI approach is that it does not treat resident involvement as a binary exposure but as a graded continuum tied to audited national data, allowing educators to characterize progression in operative complexity and link it to outcomes with unusual granularity. The study’s authors suggest that QITI may serve as a valuable platform for competency-based surgical education and future trainee feedback systems, potentially enabling programs to benchmark their residents against national distributions and to ground promotion decisions in outcome-informed evidence, while acknowledging that outcome data must always be interpreted alongside direct assessments of technical skill and clinical judgment.

For a profession in which the central paradox has always been that expertise is acquired by doing, and doing carries risk, the study offers a data-driven path through that tension. By demonstrating that nearly one and a half million resident-linked cases can be collected, risk-adjusted, and analyzed at national scale, the American College of Surgeons team has shown that the machinery built to make surgery safer for patients can simultaneously make education more transparent, more evidence-based, and more closely aligned with the realities surgeons face after graduation. The residual signals associated with the most senior trainees serve less as a warning than as a reminder that context matters: complexity, not competence, drives many of the differences that raw numbers reveal. As surgical education continues its shift toward competency-based and outcomes-informed models, the Quality In-Training Initiative stands as evidence that the data infrastructure for that transformation already exists, measured one case at a time across the operating rooms of America.

Subject of Research: The American College of Surgeons Quality In-Training Initiative as a national platform linking surgical resident participation to risk-adjusted patient outcomes for quality improvement education

Article Title: How the American College of Surgeons Quality In-Training Initiative helps quality improvement education focusing on safety: a national review of 1,412,068 surgeon trainee cases

Article References: Smolkin, C. O., Hobika, G., Grieco, A., Matthews, A., Fordham, M. J., Sfakianos, M. G., Terhune, K., Kelz, R. R., & Ko, C. Y. (2026). How the American College of Surgeons Quality In-Training Initiative helps quality improvement education focusing on safety: a national review of 1,412,068 surgeon trainee cases. Global Surgical Education – Journal of the Association for Surgical Education, 5(1), Article 178. https://doi.org/10.1007/s44186-026-00583-7

Image Credits: AI Generated

DOI: 10.1007/s44186-026-00583-7

Keywords: surgical education, resident outcomes, ACS NSQIP, Quality In-Training Initiative, quality improvement, patient safety, risk adjustment, competency-based education, surgical training, postoperative complications, graduate medical education, outcomes research