Statistics and risk
Per-protocol analysis
An analysis including only participants who sufficiently followed the study protocol.
What it means
Definition
Per-protocol analysis. Per-protocol analysis can estimate effect under ideal adherence, but it may reintroduce bias because people who follow protocols can differ from those who do not.
What it can tell you
It can help clarify what sort of evidence or claim is being discussed.
What it cannot tell you
It cannot, by itself, prove that the headline is accurate or clinically important.
Headline trap
Why this matters in headlines
A dramatic per-protocol result should be compared with the intention-to-treat result.