Original article|Articles in Press

Monitoring performance in laparoscopic gastric bypass surgery using risk-adjusted cumulative sum at 2 high-volume centers

Published:February 14, 2023DOI:


      • Risk-adjusted cumulative sum (RA-CUSUM) adjusts for clinical risk factors to identify performance outliers in real-time.
      • RA-CUSUM is applicable to quality improvement/root-cause analysis in bariatric surgery.



      Traditional surgical outcomes are measured retrospectively and intermittently, limiting opportunities for early intervention.


      The objective of this study was to use risk-adjusted cumulative sum (RA-CUSUM) to track perioperative surgical outcomes for laparoscopic gastric bypass. We hypothesized that RA-CUSUM could identify performance variations between surgeons.


      Two mid-Atlantic quaternary care academic centers.


      Patient-level data from the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP) were abstracted for laparoscopic gastric bypasses performed by 3 surgeons at 2 high-volume centers from 2014 to 2021. Estimated probabilities of serious complications, reoperation, and readmission were derived from the MBSAQIP risk calculator. RA-CUSUM curves were generated to signal observed-to-expected odds ratios (ORs) of 1.5 (poor performance) and .5 (superior performance). Control limits were set based on a false positive rate of 5% (α = .05).


      We included 1192 patients: Surgeon A = 767, Surgeon B = 188, and Surgeon C = 237. Overall rates of serious complications, 30-day reoperations, and 30-day readmissions were 3.9%, 2.5%, and 5.2% respectively, with expected rates of 4.7%, 2.2%, and 5.8%. RA-CUSUM signaled lower-than-expected (OR < .5) rates of readmission and serious complication in Surgeon A, and higher-than-expected (OR > 1.5) readmission rate in Surgeon C. Surgeon A further demonstrated an early period of higher-than-expected (OR > 1.5) reoperation rate before April 2015, followed by superior performance thereafter (OR < .5). Surgeon B’s performance generally reflected expected standards throughout the study period.


      RA-CUSUM adjusts for clinical risk factors and identifies performance outliers in real-time. This approach to analyzing surgical outcomes is applicable to quality improvement, root-cause analysis, and surgeon incentivization.


      To read this article in full you will need to make a payment

      Purchase one-time access:

      Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
      One-time access price info
      • For academic or personal research use, select 'Academic and Personal'
      • For corporate R&D use, select 'Corporate R&D Professionals'


      Subscribe to Surgery for Obesity and Related Diseases
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect


        • Birkmeyer J.
        • Shahian D.
        • Dimick J.
        • et al.
        Blueprint for a new American College of Surgeons: national surgical quality improvement program.
        J Am Coll Surg. 2008; 207: 777-782
        • Khuri S.
        • Daley J.
        • Henderson W.
        The comparative assessment and improvement of quality of surgical care in the Department of Veterans Affairs.
        Arch Surg. 2002; 137: 20-27
        • Massarweh N.
        • Chen V.
        • Rosen T.
        • et al.
        Comparative effectiveness of risk-adjusted cumulative sum and periodic evaluation for monitoring hospital perioperative mortality.
        Med Care. 2021; 59: 639-645
        • Keroack M.
        • Youngberg B.
        • Cerese J.
        • et al.
        Organizational factors associated with high performance in quality and safety in academic medical centers.
        Acad Med. 2007; 82: 1178-1186
        • Page E.
        Continuous inspection schemes.
        Biometrika. 1954; 41: 100-115
        • Hu Y.
        • Puri V.
        • Crabtree T.
        • et al.
        Attaining proficiency with endobronchial ultrasound-guided transbronchial needle aspiration.
        J Thorac Cardiovasc Surg. 2013; 146: 1387-1392
        • Renaud M.
        • Reibel N.
        • Zarnegar R.
        • et al.
        Multifactorial analysis of the learning curve for totally robotic Roux-en-Y gastric bypass for morbid obesity.
        Obes Surg. 2013; 23: 1753-1760
        • Hu Y.
        • Jolissaint J.
        • Ramirez A.
        • Gordon R.
        • Yang Z.
        • Sawyer R.G.
        Cumulative sum: a proficiency metric for basic endoscopic training.
        J Surg Res. 2014; 192: 62-67
        • Hu Y.
        • Brooks K.
        • Kim H.
        • et al.
        Adaptive simulation training using cumulative sum: a randomized prospective trial.
        Am J Surg. 2016; 211: 377-383
        • Hu Y.
        • Warren H.
        • McMurry T.
        • et al.
        Cumulative sum: an individualized proficiency metric for laparoscopic fundamentals.
        J Pediatr Surg. 2016; 51: 598-602
        • Song M.
        • Tokuda Y.
        • Nakayama T.
        • Hattori K.
        • Hirai M.
        Safe launching of a newly appointed cardiac surgery unit at a low-volume hospital with the use of cumulative sum analysis.
        Circ J. 2008; 72: 437-440
        • Grochowiecki T.
        • Jakimowicz T.
        • Grabowska-Derlatka L.
        • Szmidt J.
        Quality of pancreatic transplant program assessment of using a risk-adjusted cumulative sum chart: experience from a single small center.
        Transplant Proc. 2014; 46: 2810-2814
        • Schrem H.
        • Volz S.
        • Koch H.
        • et al.
        Statistical approach to quality assessment in liver transplantation.
        Langenbecks Arch Surg. 2018; 403: 61-71
        • Filce C.
        • Hyett J.
        • Sahota W.K.
        • McLennan A.
        Developing a quality assurance program for transvaginal cervical length measurement at 18-21 weeks’ gestation.
        Aust N Z J Obstet Gynaecol. 2020; 60: 55-62
        • Snyder J.
        • Salkowski N.
        • Zaun D.
        • et al.
        New quality monitoring tools provided by the scientific registry of transplant recipients: CUSUM.
        Am J Transplant. 2014; 14: 515-523
        • Ozoy Z.
        • Cemir E.
        Which bariatric procedure is the most popular in the world? a bibliometric comparison.
        Obes Surg. 2018; 28: 2339-2352
        • Steiner S.
        • Cook R.
        • Farewell V.
        • Treasure T.
        Monitoring surgical performance using risk-adjusted cumulative sum charts.
        Biostatistics. 2000; 1: 441-452
        • Lim T.
        • Soraya A.
        • Ding L.
        • Morad Z.
        Assessing doctors’ competence: application of CUSUM technique in monitoring doctors’ performance.
        Int J Qual Health Care. 2002; 14: 251-258
        • Begun A.
        • Kulinskaya E.
        • MacGregor A.
        Risk-adjusted CUSUM control charts for shared frailty survival models with application to hip replacement outcomes: a study using the NJR dataset.
        BMC Med Res Methodol. 2019; 19: 1-15
        • Moloo H.
        • Lamb T.
        • Sundaresan S.
        • et al.
        Leveraging financial incentives and behavioural economics to engage physicians in achieving quality-improvement process measures.
        Can J Surg. 2022; 65: E290-E295
        • Horton-Jones M.
        • Marsh E.
        • Fumarola S.
        • Wright-White H.
        • McSherry W.
        • Rowson T.
        Using deep dive methodology to investigate an increased incidence of hospital-acquired avoidable category 2 and 3 pressure ulcers.
        Healthcare (Basel). 2019; 7: 59
        • Gallivan S.
        • Davis K.
        • Stark J.
        Early identification of divergent performance in congenital cardiac surgery.
        Eur J Cardiothorac Surg. 2001; 20: 1214-1219
        • Hannan E.L.
        • Samadashvili Z.
        • Cozzens K.
        • et al.
        Out-of-hopsital 30-day deaths after cardiac surgery are often underreported.
        Ann Thorac Surg. 2020; 110: 183-188
        • Cooper M.A.
        • Ibrahim A.
        • Lyu H.
        • Makary M.A.
        Underreporting of robotic surgery complicaitons.
        J Healthc Qual. 2015; 37: 133-138
        • Healey M.A.
        • Shackford S.R.
        • Osler T.M.
        • Rogers F.B.
        • Burns E.
        Complications in surgical patients.
        Arch Surg. 2002; 137: 611-618