Research Journal of the Royal Society of Medicine; 2014, Vol. 107(9) 355–364 DOI: 10.1177/0141076814538788
Surgeon length of service and risk-adjusted outcomes: linked observational analysis of the UK National Adult Cardiac Surgery Audit Registry and General Medical Council Register Graeme L Hickey1,2, Stuart W Grant2,3, Nick Freemantle4, David Cunningham2, Christopher M Munsch5, Steven A Livesey6, James Roxburgh7, Iain Buchan1 and Ben Bridgewater1,2,4 1
Centre for Health Informatics, Manchester Academic Health Science Centre, University of Manchester, Manchester M13 9PL, UK National Institute for Cardiovascular Outcomes Research (NICOR), University College London, London W1T 7HA, UK 3 Department of Cardiothoracic Surgery, Manchester Academic Health Science Centre, University of Manchester, University Hospital of South Manchester, Manchester M23 9LT, UK 4 Department of Primary Care and Population Health, University College London, London NW3 2PF, UK 5 Department of Cardiothoracic Surgery, Leeds General Infirmary, Leeds LS1 3EX, UK 6 Department of Cardiac Surgery, University Hospital Southampton, Southampton SO16 6YD, UK 7 Department of Cardiothoracic Surgery, St Thomas’ Hospital, London SE1 7EH, UK Corresponding author: Ben Bridgewater. Email: [email protected] 2
Abstract Objectives: To explore the relationship between in-hospital mortality following adult cardiac surgery and the time since primary clinical qualification for the responsible consultant cardiac surgeon (a proxy for experience). Design: Retrospective analysis of prospectively collected national registry data over a 10-year period using mixedeffects multiple logistic regression modelling. Surgeon experience was defined as the time between the date of surgery and award of primary clinical qualification. Setting: UK National Health Service hospitals performing cardiac surgery between January 2003 and December 2012. Participants: All patients undergoing coronary artery bypass grafts and/or valve surgery under the care of a consultant cardiac surgeon. Main outcome measures: All-cause in-hospital mortality. Results: A total of 292,973 operations performed by 273 consultant surgeons (with lengths of service from 11.2 to 42.0 years) were included. Crude mortality increased approximately linearly until 33 years service, before decreasing. After adjusting for case-mix and year of surgery, there remained a statistically significant (p ¼ 0.002) association between length of service and in-hospital mortality (odds ratio 1.013; 95% CI 1.005–1.021 for each year of ‘experience’). Conclusions: Consultant cardiac surgeons take on increasingly complex surgery as they gain experience. With this progression, the incidence of adverse outcomes is expected to increase, as is demonstrated in this study. After adjusting for case-mix using the EuroSCORE, we observed an increased risk of mortality in patients operated on by longer serving surgeons. This finding may reflect under-adjustment for risk, unmeasured confounding or a
real association. Further research into outcomes over the time course of surgeon’s careers is required.
Keywords clinical experience, length of service, clinical performance, General Medical Council register, cardiac surgery, audit
Introduction Surgeons throughout the world are highly trained.1 Surgeons currently undergoing training in the UK first undertake a 4–6 year Bachelor’s Degree in Medicine and Surgery, followed by 2 years of foundation training, 2–3 years of core training, and more than 6 years of speciality training. Similar training times exist elsewhere.2 Postgraduate research or fellowships may extend this training. The association between surgical performance and cardiothoracic surgeon ‘experience’ has been investigated previously in trainee surgeons.3,4 The case-mix and complexity of surgery performed by newly appointed consultants is usually less complex than that of established consultants. However, as experience develops, a consultant will be assigned more complex caseloads, which inherently carry increased risk.5 Most studies define surgeon experience according to case-volume for a fixed cross-sectional study period.6–8 The received wisdom is that high volume surgeons, taken as a proxy for ‘experienced’ surgeons, will have better outcomes after adjustment for clinical and baseline risk factors. This assumption has
! The Royal Society of Medicine 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav Downloaded from jrs.sagepub.com at NANYANG TECH UNIV LIBRARY on June 5, 2015
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Journal of the Royal Society of Medicine 107(9)
multiple flaws, including that it fails to account for any well-characterised relation between experience and outcome. Also, case-volume may depend on the career point of the surgeon; for example, a highly experienced surgeon close to retirement may reduce their caseload progressively. It is also possible that ‘performance’ may change over time. In this paper, we quantify ‘experience’ of each surgeon as the time elapsed since the award of the first clinical degree from university. The aim of this research is to estimate the association of surgeon experience with in-hospital mortality in cardiac surgery, conditioning on an established risk score composed of known patient and operative factors to account for operative case-mix.
Materials and methods Cardiac surgery registry data Prospectively collected data by the Society for Cardiothoracic Surgery in Great Britain and Ireland (SCTS) were extracted from the National Adult Cardiac Surgery Audit (NACSA) registry on 20 November 2013 for all adult cardiac surgery procedures performed in the UK between 1 January 2003 and 31 December 2012. As described elsewhere, reproducible cleaning algorithms were applied to the data extract9: duplicate records and non-adult cardiac surgery entries were removed; transcriptional discrepancies were harmonised; clinical and temporal conflicts, and extreme values corrected or removed. If the recorded consultant was listed by name or initials, their General Medical Council (GMC) registration number was determined by means of direct communication with base hospitals and the GMC web portal (http://www.gmc-uk.org/doctors/register/ LRMP.asp). In a handful of records, multiple GMC registration numbers were recorded, in which case we used the first one only. If a transcriptional error was identified (e.g. missing or extra digit, transposed numbers or partially incorrectly entered numbers), we manually corrected the GMC registration number by inspection of similar ones for the corresponding hospital. Summaries of the preprocessed data are regularly returned to each unit for local validation as part of the NACSA in the UK. Definitions of database variables used for the study are available at http://www.ucl.ac.uk/nicor/audits/adultcardiacsurgery/datasets. Records were excluded if: (1) they were performed in a private hospital, due to incomplete case attainment; (2) the operation involved surgery other than coronary artery bypass grafting (CABG) or valve surgery; (3) they corresponded to a re-do cardiac operation
within the same admission spell (in which case only the record corresponding to the primary operation was retained for analysis); (4) the outcome variable was missing or (5) the named responsible consultant surgeon GMC registration number was missing. In addition, records were excluded if they corresponded to a surgeon with (6) a mean case volume of
Surgeon length of service and risk-adjusted outcomes: linked observational analysis of the UK National Adult Cardiac Surgery Audit Registry and General Medical Council Register Graeme L Hickey1,2, Stuart W Grant2,3, Nick Freemantle4, David Cunningham2, Christopher M Munsch5, Steven A Livesey6, James Roxburgh7, Iain Buchan1 and Ben Bridgewater1,2,4 1
Centre for Health Informatics, Manchester Academic Health Science Centre, University of Manchester, Manchester M13 9PL, UK National Institute for Cardiovascular Outcomes Research (NICOR), University College London, London W1T 7HA, UK 3 Department of Cardiothoracic Surgery, Manchester Academic Health Science Centre, University of Manchester, University Hospital of South Manchester, Manchester M23 9LT, UK 4 Department of Primary Care and Population Health, University College London, London NW3 2PF, UK 5 Department of Cardiothoracic Surgery, Leeds General Infirmary, Leeds LS1 3EX, UK 6 Department of Cardiac Surgery, University Hospital Southampton, Southampton SO16 6YD, UK 7 Department of Cardiothoracic Surgery, St Thomas’ Hospital, London SE1 7EH, UK Corresponding author: Ben Bridgewater. Email: [email protected] 2
Abstract Objectives: To explore the relationship between in-hospital mortality following adult cardiac surgery and the time since primary clinical qualification for the responsible consultant cardiac surgeon (a proxy for experience). Design: Retrospective analysis of prospectively collected national registry data over a 10-year period using mixedeffects multiple logistic regression modelling. Surgeon experience was defined as the time between the date of surgery and award of primary clinical qualification. Setting: UK National Health Service hospitals performing cardiac surgery between January 2003 and December 2012. Participants: All patients undergoing coronary artery bypass grafts and/or valve surgery under the care of a consultant cardiac surgeon. Main outcome measures: All-cause in-hospital mortality. Results: A total of 292,973 operations performed by 273 consultant surgeons (with lengths of service from 11.2 to 42.0 years) were included. Crude mortality increased approximately linearly until 33 years service, before decreasing. After adjusting for case-mix and year of surgery, there remained a statistically significant (p ¼ 0.002) association between length of service and in-hospital mortality (odds ratio 1.013; 95% CI 1.005–1.021 for each year of ‘experience’). Conclusions: Consultant cardiac surgeons take on increasingly complex surgery as they gain experience. With this progression, the incidence of adverse outcomes is expected to increase, as is demonstrated in this study. After adjusting for case-mix using the EuroSCORE, we observed an increased risk of mortality in patients operated on by longer serving surgeons. This finding may reflect under-adjustment for risk, unmeasured confounding or a
real association. Further research into outcomes over the time course of surgeon’s careers is required.
Keywords clinical experience, length of service, clinical performance, General Medical Council register, cardiac surgery, audit
Introduction Surgeons throughout the world are highly trained.1 Surgeons currently undergoing training in the UK first undertake a 4–6 year Bachelor’s Degree in Medicine and Surgery, followed by 2 years of foundation training, 2–3 years of core training, and more than 6 years of speciality training. Similar training times exist elsewhere.2 Postgraduate research or fellowships may extend this training. The association between surgical performance and cardiothoracic surgeon ‘experience’ has been investigated previously in trainee surgeons.3,4 The case-mix and complexity of surgery performed by newly appointed consultants is usually less complex than that of established consultants. However, as experience develops, a consultant will be assigned more complex caseloads, which inherently carry increased risk.5 Most studies define surgeon experience according to case-volume for a fixed cross-sectional study period.6–8 The received wisdom is that high volume surgeons, taken as a proxy for ‘experienced’ surgeons, will have better outcomes after adjustment for clinical and baseline risk factors. This assumption has
! The Royal Society of Medicine 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav Downloaded from jrs.sagepub.com at NANYANG TECH UNIV LIBRARY on June 5, 2015
356
Journal of the Royal Society of Medicine 107(9)
multiple flaws, including that it fails to account for any well-characterised relation between experience and outcome. Also, case-volume may depend on the career point of the surgeon; for example, a highly experienced surgeon close to retirement may reduce their caseload progressively. It is also possible that ‘performance’ may change over time. In this paper, we quantify ‘experience’ of each surgeon as the time elapsed since the award of the first clinical degree from university. The aim of this research is to estimate the association of surgeon experience with in-hospital mortality in cardiac surgery, conditioning on an established risk score composed of known patient and operative factors to account for operative case-mix.
Materials and methods Cardiac surgery registry data Prospectively collected data by the Society for Cardiothoracic Surgery in Great Britain and Ireland (SCTS) were extracted from the National Adult Cardiac Surgery Audit (NACSA) registry on 20 November 2013 for all adult cardiac surgery procedures performed in the UK between 1 January 2003 and 31 December 2012. As described elsewhere, reproducible cleaning algorithms were applied to the data extract9: duplicate records and non-adult cardiac surgery entries were removed; transcriptional discrepancies were harmonised; clinical and temporal conflicts, and extreme values corrected or removed. If the recorded consultant was listed by name or initials, their General Medical Council (GMC) registration number was determined by means of direct communication with base hospitals and the GMC web portal (http://www.gmc-uk.org/doctors/register/ LRMP.asp). In a handful of records, multiple GMC registration numbers were recorded, in which case we used the first one only. If a transcriptional error was identified (e.g. missing or extra digit, transposed numbers or partially incorrectly entered numbers), we manually corrected the GMC registration number by inspection of similar ones for the corresponding hospital. Summaries of the preprocessed data are regularly returned to each unit for local validation as part of the NACSA in the UK. Definitions of database variables used for the study are available at http://www.ucl.ac.uk/nicor/audits/adultcardiacsurgery/datasets. Records were excluded if: (1) they were performed in a private hospital, due to incomplete case attainment; (2) the operation involved surgery other than coronary artery bypass grafting (CABG) or valve surgery; (3) they corresponded to a re-do cardiac operation
within the same admission spell (in which case only the record corresponding to the primary operation was retained for analysis); (4) the outcome variable was missing or (5) the named responsible consultant surgeon GMC registration number was missing. In addition, records were excluded if they corresponded to a surgeon with (6) a mean case volume of
