In addition to the primary endpoint reported in a study, researchers may measure and report secondary endpoints as well. These are not (supposed to be) the main outcomes of the study but provide additional information to consider in balancing the benefits and risks of an intervention, such as side effects, cost savings or surrogate endpoints, such as amount of tumor shrinkage or reduction of specific symptoms.
Deeper dive
Secondary endpoints are often, but not always, listed in the study objectives with the primary endpoint. Two things journalists should look for when looking at secondary endpoints: a) Were any of them originally a primary endpoint as noted in the clinicaltrials.gov study listing? b) Do the study authors, or the press release writers, focus more on the secondary endpoint results than the primary endpoint results if the primary endpoints did not achieve the desired effect? Sometimes authors and/or press release writers will distract from a negative finding in the primary endpoint by focusing more on the secondary endpoints, but this practice should raise a red flag.