A new paper in the Lancet and related twitter thread
Using individual patient data for each trial we calculated mean 24-month BMD percent change together with fracture reductions and did a meta-regression of the association between treatment-related differences in BMD changes (percentage difference, active minus placebo) and fracture risk reduction
Many threads on the forum have covered the problems with precent change from baseline in general. Yet here is another influential result where investigators have chosen to go with percent change nonetheless.
- the post value must be linearly related to the pre value
- the variable must be perfectly transformed so that subtraction “works” and the result is not baseline-dependent
- the variable must not have floor and ceiling effects
- the variable must have a smooth distribution
- the slope of the pre value vs. the follow-up measurement must be close to 1.0 when both variables are properly transformed (using the same transformation on both)
Anyone care to comment whether BMD is a positive example of when percent change is not egregious?