Background: One of the most important recommendations of the available guidelines on studying and reporting subgroup analyses, is to pre-specify subgroups rather than define them post hoc. We therefore studied both grant proposals and their publications and compared the subgroup analyses that were pre-specified in the grant proposal to those that were finally published.
Objectives: To compare grant applications and final publications regarding subgroup analyses.
Methods: Grants awarded by the 'Netherlands Organization for Health Research and Development’ from 2001, were studied. We analyzed whether or not projects mentioned subgroups in their grant application and related publications (i.e. the final report and scientific publications). The main outcome measure was the proportion of studies in which the publications were completely in agreement with the grant proposal, i.e., subgroups that were pre-specified in the grant proposal were reported and no new subgroup analyses were introduced in the publications. Of all individual subgroups that could be identified in the included projects, we analyzed if they were pre-specified or a post-hoc finding.
Results: In 20 (25%) of the 79 included projects, publications were completely in agreement with the grant proposal. Of the 149 pre-specified subgroups, 46 (31%) were reported in the final report or scientific publications, and 143 of the 189 (76%) reported subgroups were based on post-hoc findings. For 77% of the subgroup analyses in the publications, there was no mention whether these were pre-specified or post-hoc. Justification for subgroup analysis and methods to study subgroups were rarely reported.
Conclusion: There is a large discrepancy between grant applications and final publications regarding subgroup analyses. Both non-reporting of pre-specified subgroup analyses and reporting of post-hoc subgroup analyses are common.