Ann Yellowlees

Director of Statistics at Quantics Consulting Limited

Author of: What is indirect comparison?

Ann is Director of Statistics at Quantics Consulting Ltd.  Her career to date includes lecturing in Statistics at the University of Bristol, leading the Statistics team at Shell Research, Sittingbourne and heading the Scottish Cancer Intelligence Unit of the Information & Statistics Division of NHS Scotland.  In 2002 she established Quantics as a statistical consultancy, now specialising in meta-analysis and network meta-analysis projects, as well as other areas of biostatistics, in particular bioassay development.  Ann holds a BA in Mathematics, an MSc in Applied Statistics from the University of Oxford and a PhD in Statistics from the University of Waterloo, Ontario, Canada, and has a special interest in survival methods.

Summary: What is indirect comparison?

  • Indirect comparison can be used to compare treatments that have not been directly compared with each other in a head-to-head trial. It is often used when there is no evidence or insufficient evidence from head to-head trials, or when more than two treatments are of interest.
  • Indirect comparisons are usually conducted using network meta-analysis, an extension of meta-analysis that includes more than two treatments. Network meta-analysis is also referred to as multiple-treatments meta-analysis.
  • Network meta-analysis includes indirect treatment comparison and mixed treatment comparison, although all of these terms are often used interchangeably.
  • Like meta-analysis, indirect comparison combines data from different studies (usually randomised controlled trials) in order to produce overall estimates of treatment effects. Basic assumptions required for indirect comparisons include a homogeneity assumption as per standard meta-analysis, a similarity assumption for indirect comparison and a consistency assumption for the combination of direct and indirect evidence. It is essential to fully understand these basic assumptions in order to produce valid indirect comparisons.
  • Indirect comparison is often part of the systematic review process. The validity of any indirect comparison also depends on the studies on which it is based.
  • The use of indirect comparison has increased rapidly in recent years, and indirect comparisons are now accepted by many health technology assessment agencies.