Find the primary endpoint of a trial and the result reported for it
The primary endpoint is the one outcome a trial was designed and sized to answer; everything else is secondary. Reports sometimes give the secondary results more prominence than the primary one. Ask Search+ "What was the primary endpoint, when was it measured, and what was the result?" and open the citations to read the definition in the methods and the figure in the results.
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Last updated October 2026
How to find the primary endpoint with Search+
- Upload the report and the registered protocol
The primary endpoint is fixed in the protocol and the trial registration before results are known. Put the protocol in the workspace with the report so you can check that they match.
- Ask for the definition, then the result
First ask how the primary endpoint was defined and timed. Then ask for the result reported for it. Two questions give two citations: one in the methods, one in the results.
- Separate it from secondary outcomes
Ask which outcomes were secondary or exploratory. If a headline finding in the abstract is not the primary endpoint, the citations will show it.
Questions to ask about primary endpoints
How exactly does the report define the primary endpoint?
At what time point was the primary endpoint assessed?
What result does the report give for the primary endpoint, with its confidence interval if stated?
Does the report say the primary endpoint was changed after the trial began?
If the primary endpoint is a composite, which components does it combine?
Which expected effect on the primary endpoint was the sample size calculated for?
What to look for in a primary endpoint
The sample size calculation is normally based on the primary endpoint, so it is the result the trial was best designed to detect. Secondary outcomes carry less weight.
Some trials count any of several events, such as hospitalization or death, as one endpoint. Ask which components drove the result, because they may not be equally important.
A laboratory value or imaging result can be used in place of a clinical outcome. Note whether the endpoint is a surrogate before reading much into it.
A primary endpoint that differs from the registered one is a known reporting problem. Compare the report with the protocol or registry entry.
Answers cite the passages they used, with page or section references when the report gives them, so you can read the definition and the figure yourself.
Workspace Context can tell Search+ to quote figures exactly and flag secondary outcomes, and it applies to every question in that workspace.
Endpoint wording and the follow-up to ask
| Wording you may see | What it usually signals | A follow-up question |
|---|---|---|
| "primary endpoint" or "primary outcome" | The outcome the trial was designed for | When was it measured, and how? |
| "key secondary endpoint" | An important but not primary outcome | Was it tested only if the primary endpoint was met? |
| "composite of" | Several events counted together | Which component contributed most events? |
| "change from baseline" | A continuous measure over time | What was the baseline value in each arm? |
| "non-inferiority margin" | A trial testing that a treatment is not worse by a set amount | What margin did the trial use and why? |
| "exploratory" or "post hoc" | Analyses not planned as main tests | Which results in the abstract are exploratory? |
What is a primary endpoint?
A primary endpoint is the main outcome a clinical trial is designed to measure, specified before the trial begins, used to calculate the sample size and used to judge whether the intervention met the trial's main objective.
Primary endpoint questions
Can Search+ find the primary endpoint in a long report?
Can it check whether the endpoint changed from the protocol?
Will it explain a composite endpoint?
Does it judge whether the result is clinically meaningful?
Can I compare primary endpoints across trials?
Could an answer confuse primary and secondary outcomes?
Hold the trial to its own question
Start a workspace, upload the report and protocol, and ask what the primary endpoint was and what it showed.
Start a workspace