Baseline is the first official study visit with the subject after determining that they meet the criteria for the clinical trial through the screening process. The baseline is considered the date and time of initiation of the study for that subject.

Initial clinical information collected during the baseline visit is used as a comparative measure for subsequent data obtained for the subject. The data may include demographics and study-specific measures, such as physical exams, laboratory tests, imaging, or outcome assessments, as required by the protocol.

Why is the baseline important?

Baseline data creates a reference point that allows for any changes to be tracked through the clinical trial and enables the basis of comparative evaluation.

Source: Glossary of Common Site Terms – (n.d.). Clinicaltrials.Gov. Retrieved January 7, 2022, from