Objectives Many UK primary care trusts have recently introduced eligibility criteria restricting total knee replacement (TKR) to patients with low pre-operative Oxford Knee Scores (OKS) to cut expenditure. We evaluate these criteria by assessing the cost-effectiveness of TKR compared with no knee replacement for patients with different baseline characteristics from an NHS perspective.
Design The cost-effectiveness of TKR in different patient subgroups was assessed using regression analyses of patient-level data from the Knee Arthroplasty Trial, a large, pragmatic randomised trial comparing knee prostheses.
Setting 34 UK hospitals.
Participants 2131 osteoarthritis patients undergoing TKR.
Interventions and outcome measures Costs and quality-adjusted life years (QALYs) observed in the Knee Arthroplasty Trial within 5 years of TKR were compared with conservative assumptions about the costs and outcomes that would have been accrued had TKR not been performed.
Results On average, primary TKR and 5 years of subsequent care cost £7458 per patient (SD: £4058), and patients gained an average of 1.33 (SD: 1.43) QALYs. As a result, TKR cost £5623/QALY gained. Although costs and health outcomes varied with age and sex, TKR cost <£20 000/QALY gained for patients with American Society of Anaesthesiologists grades 1–2 who had baseline OKS <40 and for American Society of Anaesthesiologists grade 3 patients with OKS <35, even with highly conservative assumptions about costs and outcomes without TKR. Body mass index had no significant effect on costs or outcomes. Restricting TKR to patients with pre-operative OKS <27 would inappropriately deny a highly cost-effective treatment to >10 000 patients annually.
Conclusions TKR is highly cost-effective for most current patients if the NHS is willing to pay £20 000–£30 000/QALY gained. At least 97% of TKR patients in England have more severe symptoms than the thresholds we have identified, suggesting that further rationing by OKS is probably unjustified.
Trial registration number ISRCTN 45837371.
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Protocol: Available at http://www.hta.ac.uk/protocols/199500100001.pdf
To cite: Dakin H, Gray A, Fitzpatrick R, et al. Rationing of total knee replacement: a cost-effectiveness analysis on a large trial data set. BMJ Open 2012;2:e000332. doi:10.1136/bmjopen-2011-000332
Funding The Knee Arthroplasty Trial is funded by the NIHR Health Technology Assessment Programme (project number 95/10/01). Additional funding for research support in clinical centres was provided by Howmedica Osteonics; Zimmer; DePuy, a Johnson and Johnson company; Corin Medical; Smith and Nephew Healthcare; Biomet Merck and Wright Cremascoli. The Health Economics Research Centre obtains support from the National Institute of Health Research. The Health Services Research Unit is core funded by the Chief Scientist Office of the Scottish Government Health Directorates. The Biomedical Research Unit at Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences is funded by the National Institute of Health Research. The authors conducted the research independently of all funding organisations. The funders had no role in the collection, analysis or interpretation of data, writing of the manuscript or the decision to publish. The authors had full access to all the data (including statistical reports and tables) in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Competing interests All authors have completed the Unified Competing Interest form at http://www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare no support from any organisation for the submitted work with the exception of those declared in the funding statement. AG, RF and GM declare that they have no financial relationships with any organisations that might have an interest in the submitted work in the previous 3 years and no other relationships or activities that could appear to have influenced the submitted work. DM receives royalties paid to him by Biomet but both declare that they have no other financial relationships with any organisations that might have an interest in the submitted work in the previous 3 years and no other relationships or activities that could appear to have influenced the submitted work.
Ethics approval The KAT trial was approved by the Multi Centre Research Ethics Committee for Scotland in November 1998 (research protocol MREC/98/0/100) and was approved by the Local Research Ethics Committees in each study centre recruiting trial participants. Further details are available on request.
Contributors HD, AG and DM conceived and developed the principles and methods underpinning the current analysis. GM was involved in primary data collection and database management, while HD conducted the analysis under AG's supervision and guidance from DM, GM and RF. HD drafted the manuscript with input from all other authors; all authors have approved the final manuscript and were involved in the interpretation of results. The KAT trial was conceived, designed and run by the KAT trial group, which comprised Suzanne Breeman, Marion Campbell, HD, Jackie Ellington, Nick Fiddian, RF, Adrian Grant, AG, Linda Johnston, GM, Richard Morris and DM.
Data sharing statement See http://bmjopen.bmj.com/site/about/resources/datamanagement.xhtml.