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Can joint replacement reduce cardiovascular risk?

BMJ 2013; 347 doi: (Published 20 November 2013) Cite this as: BMJ 2013;347:f6651
  1. Mohammad Ehsanul Karim, PhD candidate
  1. 1Department of Statistics, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
  1. ehsan{at}

The role of propensity score matching and landmark analysis in interpreting observational studies of treatments

Randomised trials are usually the best way to evaluate treatments, but observational designs can also provide useful insights into the effects of a particular treatment, as long as researchers use the appropriate statistical tools to help overcome the limitations of these studies. The paper by Ravi and colleagues (doi:10.1136/bmj.f6187),1 which reported an association between total joint arthroplasty and a reduced risk of serious cardiovascular events over a median follow-up of seven years, is a good illustration of two of these techniques: propensity score matching2 and landmark analysis.3

Patients are not randomised in observational comparative effectiveness studies. Lack of randomisation may contribute to differences in baseline characteristics of treated and untreated patients, including important prognostic factors such as age, sex, and comorbidities. Techniques such as propensity score matching make it possible to iron out these differences, so meaningful comparisons between treated and untreated groups can be made. The score, which is derived using multivariate logistic …

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