Critical appraisal in and of IPD meta-analysis projects
Biases
- An important part of an IPD meta-analysis project is to examine the robustness of IPD meta-analysis results to potential biases that could occur
- Publication-related biases hide relevant trials and data, often those with ‘negative’ findings (e.g. statistically non-significant results). As for any type of review, this could lead to IPD meta-analysis results being biased toward favourable effects
- Availability bias is a concern if IPD are obtained from only a subset of the trials from which requested, and the provision of IPD is linked to trial findings. This may also make the IPD meta-analysis results biased, although the direction of bias is hard to predict
- These issues may lead to small-study effects in the IPD meta-analysis, where smaller trials exhibit different (often greater) effect estimates than larger trials. Small-study effects are revealed by asymmetry in a funnel plot, but they may also arise due to factors that cause between-trial heterogeneity
- The impact of availability bias can be investigated by utilising aggregate data from non-IPD trials in sensitivity analyses; however, obtaining suitable aggregate data may be problematic, and the process may simply reinforce why IPD was required in the first place
- Other sensitivity analyses may be needed to examine bias concerns. In particular, analyses restricted to trials at low risk of bias investigate whether the meta-analysis conclusions are influenced by trial quality
References:
- Ahmed I, Sutton AJ, Riley RD. Assessment of publication bias, selection bias, and unavailable data in meta-analyses using individual participant data: a database survey. BMJ 2012; 344: d7762.
- Sterne JAC, Sutton AJ, Ioannidis JPA, Terrin N, Jones DR, Lau J, et al. Recommendations for examining and interpreting funnel plot asymmetry in meta-analyses of randomised controlled trials. BMJ 2011; 342:d4002.
- Riley RD. Commentary: Like it and lump it? Meta-analysis using individual participant data. Int J Epidemiol 2010; 39(5):1359-1361.
- Stewart L, Tierney J, Burdett S. Do Systematic Reviews Based on Individual Patient Data Offer a Means of Circumventing Biases Associated with Trial Publications? In: Rothstein HR, Sutton AJ, Borenstein M, editors. Publication Bias in Meta-Analysis: Prevention, Assessment and Adjustments. Chichester, UK.: John Wiley & Sons, Ltd., 2006.
- Clarke MJ, Stewart LA. Obtaining data from randomised controlled trials: how much do we need for reliable and informative meta-analyses? In: Chalmers I, Altman DG, editors. Systematic reviews. London: BMJ Publishing, 1995:37-47.