Journal of Public Health Advance Access originally published online on September 1, 2006
Journal of Public Health 2006 28(4):396-397; doi:10.1093/pubmed/fdl054
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Correspondence |
Inappropriate lack of stratification by elective or emergency operation status and missing information on important confounders
Georgios Lyratzopoulos
Consultant in Public Health East of England Strategic Health Authority, Victoria House, Capital Park, Fulbourn, Cambridge CB1 5XB, UK E-mail: georgios.lyratzopoulos{at}eoe.nhs.uk
Sirs,
I would wish to comment on the article by Judge et al.1 and the observed association between volume and outcomes for hip and knee joint replacement surgery in England.
The authors examine the effect of volume of activity at a hospital (as opposed to individual surgeon) level. Rephrasing the title as ‘...centre volume of activity and training status...’ and omitting the potentially misleading words ‘surgical volume’ would have been more precise.
The authors refer to studies examining the volume–outcome relationship in a rather selective fashion, suggesting that most of the evidence relates to cardiac revascularization surgery. It is not clear why congruent evidence relating to a multiplicity of different procedures and conditions, including surgery for many different cancer sites as well as specialist surgery for ‘benign’ conditions such as morbid obesity,2 is ignored.
Emergency joint replacement operations confer a high excess risk of 30-day mortality [the authors report an adjusted odds ratio (OR) value >5]. Persons requiring emergency hip replacement usually suffer from fractures of the femoral neck or head, whereas persons requiring a hip replacement electively usually suffer from chronic osteoarthritis—two patient subgroups with entirely different characteristics, care pathways and risk profiles. It would have therefore been much more informative if the analysis was stratified for elective and emergency operations and presented separately. Use of regression techniques, even after the examination of potential for effect modification between two variables, does not obviate the need for the description of stratified results, when it is clearly appropriate.
In interpreting the findings, the authors seem to ignore the potential relevance of a wide range of important confounders, including volume of activity at the individual surgeon level and availability and quality of post-operative supportive care (including specialist nursing and physiotherapy). Clearly, and as this study also reiterates, procedures on patients undergoing emergency hip replacement (for fractures of the femoral neck or head) are responsible for a disproportionately large number of deaths. For such patients, timely access to surgery is also important, and the availability of medical and anaesthetic expertise and support can be important in enabling access to surgery.3
In conclusion, in relation to hip replacements, this study examines the potential relationship between volume and outcomes at a hospital level only, rather inappropriately aggregating emergency and elective presentations and not fully accounting for the range of other important variables, particularly in relation to emergency presentations. As such, it presents policy makers with evidence that is extremely difficult to translate into any meaningful, and most importantly, evidence-based action.
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References |
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 TOP References |
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- Judge Al, Chard J, Learnmonth I et al. The effects of surgical volumes and training centre status on outcomes following total joint replacement: analysis of the Hospital Episode Statistics for England. J Public Health 2006;28(2):116–24.
- Flum DR, Salem L, Elrod JA et al. Early mortality among Medicare beneficiaries undergoing bariatric surgical procedures. JAMA 2005;294:1903–8.
[Abstract/Free Full Text] - Charalambous CP, Yarwood S, Paschalides C et al. Factors delaying surgical treatment of hip fractures in elderly patients. Ann R Coll Surg Engl 2003;85(2):117–9.
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