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. 1995 Jul 15;311(6998):151–155. doi: 10.1136/bmj.311.6998.151

Volume and outcome in coronary artery bypass graft surgery: true association or artefact?

A J Sowden 1, J J Deeks 1, T A Sheldon 1
PMCID: PMC2550219  PMID: 7613425

Abstract

OBJECTIVES--To examine the evidence for a relation between volume of coronary artery bypass graft surgery and hospital death rates, and to assess the degree to which this could be due to confounding because of differences in case mix. SUBJECTS--People receiving coronary artery bypass graft surgery in the United States. DESIGN--A systematic review of empirical studies examining the relation between volume and outcome of coronary artery bypass graft surgery. Studies were scored according to degree of adjustment for case mix. Above 200 procedures a year was regarded as high volume. RESULTS--Fifteen studies were identified, all of which used observational data from the United States for 1972-92. Six were included in the analysis, one was included in a sensitivity analysis, and eight were excluded because of duplicate analyses of data sources and methods of reporting results. The seven studies analysed reported a reduced mortality with increased volume. Studies with better adjustment for case mix, however, indicated less reduction in mortality with increased volume (P = 0.04). The apparent advantages of higher volume also decreased over time (P < 0.001). CONCLUSIONS--The evidence for reduced mortality in hospitals with a high volume of coronary artery bypass graft surgery is based entirely on observational studies. These studies may have over-estimated the benefit of increased volume because of poor adjustment for case mix. It signals the need for caution in interpreting the results of observational studies that examine the relation between volume and outcome.

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Selected References

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  1. Banta D., Bos M. The relation between quantity and quality with coronary artery bypass graft (CABG) surgery. Health Policy. 1991 Jun;18(1):1–10. doi: 10.1016/0168-8510(91)90139-o. [DOI] [PubMed] [Google Scholar]
  2. Black N., Johnston A. Volume and outcome in hospital care: evidence, explanations and implications. Health Serv Manage Res. 1990 Jul;3(2):108–114. doi: 10.1177/095148489000300205. [DOI] [PubMed] [Google Scholar]
  3. DesHarnais S. I., McMahon L. F., Jr, Wroblewski R. T., Hogan A. J. Measuring hospital performance. The development and validation of risk-adjusted indexes of mortality, readmissions, and complications. Med Care. 1990 Dec;28(12):1127–1141. [PubMed] [Google Scholar]
  4. Dickersin K., Min Y. I., Meinert C. L. Factors influencing publication of research results. Follow-up of applications submitted to two institutional review boards. JAMA. 1992 Jan 15;267(3):374–378. [PubMed] [Google Scholar]
  5. Farley D. E., Ozminkowski R. J. Volume-outcome relationships and in-hospital mortality: the effect of changes in volume over time. Med Care. 1992 Jan;30(1):77–94. doi: 10.1097/00005650-199201000-00009. [DOI] [PubMed] [Google Scholar]
  6. Garnick D. W., Luft H. S., McPhee S. J., Mark D. H. Surgeon volume vs hospital volume: which matters more? JAMA. 1989 Jul 28;262(4):547–548. [PubMed] [Google Scholar]
  7. Hannan E. L., Kilburn H., Jr, Bernard H., O'Donnell J. F., Lukacik G., Shields E. P. Coronary artery bypass surgery: the relationship between inhospital mortality rate and surgical volume after controlling for clinical risk factors. Med Care. 1991 Nov;29(11):1094–1107. [PubMed] [Google Scholar]
  8. Hannan E. L., Kilburn H., Jr, Racz M., Shields E., Chassin M. R. Improving the outcomes of coronary artery bypass surgery in New York State. JAMA. 1994 Mar 9;271(10):761–766. [PubMed] [Google Scholar]
  9. Hannan E. L., O'Donnell J. F., Kilburn H., Jr, Bernard H. R., Yazici A. Investigation of the relationship between volume and mortality for surgical procedures performed in New York State hospitals. JAMA. 1989 Jul 28;262(4):503–510. [PubMed] [Google Scholar]
  10. Hannan E. L., Siu A. L., Kumar D., Kilburn H., Jr, Chassin M. R. The decline in coronary artery bypass graft surgery mortality in New York State. The role of surgeon volume. JAMA. 1995 Jan 18;273(3):209–213. [PubMed] [Google Scholar]
  11. Higgins T. L., Estafanous F. G., Loop F. D., Beck G. J., Blum J. M., Paranandi L. Stratification of morbidity and mortality outcome by preoperative risk factors in coronary artery bypass patients. A clinical severity score. JAMA. 1992 May 6;267(17):2344–2348. [PubMed] [Google Scholar]
  12. Hlatky M. A., Califf R. M., Harrell F. E., Jr, Lee K. L., Mark D. B., Pryor D. B. Comparison of predictions based on observational data with the results of randomized controlled clinical trials of coronary artery bypass surgery. J Am Coll Cardiol. 1988 Feb;11(2):237–245. doi: 10.1016/0735-1097(88)90086-1. [DOI] [PubMed] [Google Scholar]
  13. Houghton A. Variation in outcome of surgical procedures. Br J Surg. 1994 May;81(5):653–660. doi: 10.1002/bjs.1800810508. [DOI] [PubMed] [Google Scholar]
  14. Hughes R. G., Hunt S. S., Luft H. S. Effects of surgeon volume and hospital volume on quality of care in hospitals. Med Care. 1987 Jun;25(6):489–503. doi: 10.1097/00005650-198706000-00004. [DOI] [PubMed] [Google Scholar]
  15. Luft H. S., Bunker J. P., Enthoven A. C. Should operations be regionalized? The empirical relation between surgical volume and mortality. N Engl J Med. 1979 Dec 20;301(25):1364–1369. doi: 10.1056/NEJM197912203012503. [DOI] [PubMed] [Google Scholar]
  16. Luft H. S., Garnick D. W., Mark D. H., Peltzman D. J., Phibbs C. S., Lichtenberg E., McPhee S. J. Does quality influence choice of hospital? JAMA. 1990 Jun 6;263(21):2899–2906. [PubMed] [Google Scholar]
  17. Luft H. S., Hunt S. S., Maerki S. C. The volume-outcome relationship: practice-makes-perfect or selective-referral patterns? Health Serv Res. 1987 Jun;22(2):157–182. [PMC free article] [PubMed] [Google Scholar]
  18. Maerki S. C., Luft H. S., Hunt S. S. Selecting categories of patients for regionalization. Implications of the relationship between volume and outcome. Med Care. 1986 Feb;24(2):148–158. doi: 10.1097/00005650-198602000-00006. [DOI] [PubMed] [Google Scholar]
  19. Malenka D. J., McLerran D., Roos N., Fisher E. S., Wennberg J. E. Using administrative data to describe casemix: a comparison with the medical record. J Clin Epidemiol. 1994 Sep;47(9):1027–1032. doi: 10.1016/0895-4356(94)90118-x. [DOI] [PubMed] [Google Scholar]
  20. Orchard C. Comparing healthcare outcomes. BMJ. 1994 Jun 4;308(6942):1493–1496. doi: 10.1136/bmj.308.6942.1493. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Riley G., Lubitz J. Outcomes of surgery among the Medicare aged: surgical volume and mortality. Health Care Financ Rev. 1985 Fall;7(1):37–47. [PMC free article] [PubMed] [Google Scholar]
  22. Rosenfeld K., Luft H. S., Garnick D. W., McPhee S. J. Changes in patient characteristics and surgical outcomes for coronary artery bypass surgery 1972-82. Am J Public Health. 1987 Apr;77(4):498–500. doi: 10.2105/ajph.77.4.498. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Showstack J. A., Rosenfeld K. E., Garnick D. W., Luft H. S., Schaffarzick R. W., Fowles J. Association of volume with outcome of coronary artery bypass graft surgery. Scheduled vs nonscheduled operations. JAMA. 1987 Feb 13;257(6):785–789. [PubMed] [Google Scholar]
  24. Sloan F. A., Perrin J. M., Valvona J. In-hospital mortality of surgical patients: is there an empiric basis for standard setting? Surgery. 1986 Apr;99(4):446–454. [PubMed] [Google Scholar]
  25. Stiller C. A. Centralised treatment, entry to trials and survival. Br J Cancer. 1994 Aug;70(2):352–362. doi: 10.1038/bjc.1994.306. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Thompson S. G. Controversies in meta-analysis: the case of the trials of serum cholesterol reduction. Stat Methods Med Res. 1993;2(2):173–192. doi: 10.1177/096228029300200205. [DOI] [PubMed] [Google Scholar]
  27. Whitehead A., Whitehead J. A general parametric approach to the meta-analysis of randomized clinical trials. Stat Med. 1991 Nov;10(11):1665–1677. doi: 10.1002/sim.4780101105. [DOI] [PubMed] [Google Scholar]
  28. Williams S. V., Nash D. B., Goldfarb N. Differences in mortality from coronary artery bypass graft surgery at five teaching hospitals. JAMA. 1991 Aug 14;266(6):810–815. [PubMed] [Google Scholar]
  29. Zelen J., Bilfinger T. V., Anagnostopoulos C. E. Coronary artery bypass grafting. The relationship of surgical volume, hospital location, and outcome. N Y State J Med. 1991 Jul;91(7):290–292. [PubMed] [Google Scholar]

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