Accepted answer
Only what the 2.4 mg arm reported, and the denominator is that arm rather than the trial. Adverse-event tables are published per arm, so the 2.4 mg incidence of injection-site erythema has its own numerator and its own denominator, and pooling it with the other arms produces a figure that describes nobody. Two further deductions before you use it. Subtract the placebo arm — injection-site erythema occurs in people who received nothing, and the difference is the part attributable to the drug. And check whether REDEFINE-1 counted events or counted participants: one participant with six episodes is one row in a participant count and six in an event count, and the two get quoted interchangeably. Nothing here is medical advice.
The trial answers a narrower question than the headline suggests, and the narrowing is where the useful information is.
Placebo arms in this class are not nothing. Lifestyle-intervention placebo arms in the major obesity trials commonly lose two to three per cent of body weight, so an active-arm figure quoted without its comparator overstates the drug effect by roughly that much.
Specifically, duration decides what can be seen. A 68-week trial can measure weight and glycaemia; it cannot measure anything whose event rate is one per cent per year without enrolling tens of thousands.
Meta-analyses in this area are dominated by whichever trial contributed the most participants, so read the forest plot rather than the summary estimate.
The short version: check the endpoint, check the comparator, check who was excluded, then look at the number.
edited 24 Jun 2025 by pieter_maas — added the citation requested in comments