Background: Individual participant data (IPD) meta-analysis is an increasingly used approach for synthesizing and investigating treatment effect estimates. Over the past few years, numerous methods for conducting an IPD meta-analysis (IPD-MA) have been proposed, often making different assumptions and modeling choices while addressing a similar research question. As a consequence, meta-analytic models sometimes lead to conflicting results, which casts doubt on their utility and validity.
Objectives: To assist researchers to choose appropriate methods and provide recommendations on their implementation when planning and conducting an IPD-MA.
Methods: We conducted a literature review to provide an overview of methods for performing an IPD-MA using evidence from clinical trials or non-randomized studies when investigating treatment efficacy. Articles were eligible if they presented statistical methods, results from empirical case studies or provided methodological guidance.
Results: A total of 153 records (out of 3360 unique records identified) were included.
Conclusions: IPD-MA offer numerous advantages over meta-analyses that are solely based on published AD. There is substantial, although disperse, information on how IPD-MA should be conducted. This review may help systematic reviewers with a limited background in medical statistics to identify relevant methods for their IPD-MA.