Intended for healthcare professionals

Rapid response to:


Validity of indirect comparison for estimating efficacy of competing interventions: empirical evidence from published meta-analyses

BMJ 2003; 326 doi: (Published 01 March 2003) Cite this as: BMJ 2003;326:472

Rapid Response:

Adjusted indirect comparison is a logical extension of utilising data from RCTs

The empirical evidence summarised in our paper suggested that
adjusted indirect comparison usually but not always agree with the results
of head to head randomised trials. This finding is perhaps not a surprise
to people so that "nobody had commented yet" except Sacristan, Prieto and
Galende (1).

Sacristan and colleagues mentioned that adjusted indirect comparison
have not been included in the ranking of research evidence. In fact, the
method has been considered in evidence ranking, for example, levels of
evidence for comparing the efficacy of drugs within the same class (2).
McAlister and colleagues recommended that evidence could be ranked from
level 1 to level 4, according to comparison method, similarity of study
patients, clinical importance of outcomes, and threats to validity. Level
2 or level 3 evidence may be based on adjusted indirect comparison using
placebo as a common comparator.

It is an overstatement to say that adjusted indirect comparison is "a
new sacrilege in clinical research" (1). The adjusted indirect comparison
has been explicitly or implicitly used in the assessment of healthcare
interventions. Actually, we consider the adjusted indirect comparison as a
logical extension of utilising precious data from randomised trials. The
validity of adjusted indirect comparison depends on the validity of RCTs
involved. For the adjusted indirect comparison to be valid, we also need
to assess study characteristics that are related to the exchangeability of
results across trials, including patient characteristics, methodological
quality, endpoint definitions, and adherence rates.

Where possible head to head RCTs may always be preferred. However, we
do agree with Sacristan and colleagues that adjusted indirect comparison
needs more formal attention in medical research.


1. Sacristan JA, Prieto L, Galende I. Indirect comparisons: a new
sacrilege in clinical research? Rapid responses to: Validity of indirect
comparison for estimating efficacy of competing interventions: empirical
evidence from published meta-analyses. 8 April 2003

2. McAlister F, Laupacis A, Wells G, Sackett D. Users' Guides to the
Medical Literature: XIX. Applying clinical trial results B. Guidelines for
determining whether a drug is exerting (more than) a class effect. JAMA

Competing interests:  
Authors of the original paper

Competing interests: No competing interests

17 April 2003
Fujian Song
Senior Research Fellow
Douglas G. Altman, Anne-Mrie Glenny, Jonathan J. Deeks
Department of Public Health and Epidemiology, University of Birmingham, Birmingham, UK b15 2TT