The use of percentage change from baseline as an outcome in a controlled trial is statistically inefficient: a simulation study.

ABSTRACT:

Background

Many randomized trials involve measuring a continuous outcome - such as pain, body weight or blood pressure - at baseline and after treatment. In this paper, I compare four possibilities for how such trials can be analyzed: post-treatment; change between baseline and post-treatment; percentage change between baseline and post-treatment and analysis of covariance (ANCOVA) with baseline score as a covariate. The statistical power of each method was determined for a hypothetical randomized trial under a range of correlations between baseline and post-treatment scores.

Results

ANCOVA has the highest statistical power. Change from baseline has acceptable power when correlation between baseline and post-treatment scores is high;when correlation is low, analyzing only po

SUBMITTER: Vickers AJ 

PROVIDER: S-EPMC34605 | biostudies-literature | 2001

REPOSITORIES: biostudies-literature