From science to practice. Meta-analyses using individual patient data are needed

In this issue ofTHE JOURNAL, Jeng et al¹report discrepancies between the results of meta-analyses using aggregate data available from the literature (MAL) and meta-analyses using individual patient data (MAP). This may be seen as further grounds for mistrusting meta-analysis in general²,³and MAL in particular,⁴but before deciding that all meta-analyses are an exercise in "mega-silliness,"⁵consider the alternatives. See also p 830. The key characteristic of MAPs is the use of individual patient data (IPD). Meta-analyses using aggregate data also can, and frequently do, include unpublished data, so the termIPD meta-analysesis preferable to avoid confusing issues relating to using IPD and issues relating to using unpublished data. IPD meta-analyses require international cooperation between the individuals and groups who have conducted relevant trials and a considerable amount of time, personnel, and financial resources.⁶These global collaborative endeavors have yielded important information