Change score or follow-up score? Choice of mean difference estimates could impact meta-analysis conclusions

Abstract

Objectives: In randomized controlled clinical trials, continuous outcomes are typically measured at both baseline and follow-up, and mean difference could be estimated using the change scores from baseline or the follow-up scores. This study assesses the impact of using change score vs. follow-up score on the conclusions of meta-analyses.

Study design and setting: A total of 63 meta-analyses from six comparative effectiveness reviews were included. The combined mean difference was estimated using a random-effects model, and we also evaluated whether the impact qualitatively varied by alternative random-effects estimates.

Results: Based on the Dersimonian-Laird (DL) method, using the change vs. the follow-up score led to five meta-analyses (7.9%) showing discrepancy in conclusions. Based on the profile likelihood (PL) method, nine (14.3%) showed discrepancy in conclusions. Using change score was more likely to show a significant difference in effects between interventions (DL method: 4 of 5; PL method: 7 of 9). A significant difference in baseline scores did not necessarily lead to discrepancies in conclusions.

Conclusions: Using the change vs. the follow-up score could lead to important discrepancies in conclusions. Sensitivity analyses should be conducted to check the robustness of results to the choice of mean difference estimates.

Keywords: Baseline difference; Change score; Follow-up score; Mean difference; Meta-analysis; Random-effects estimates.