What does the term 'baseline' refer to in clinical trials?

The term 'baseline' in clinical trials refers to the last measurement taken before the intervention or treatment starts. This data serves as a reference point against which the effects of the treatment can be compared. Establishing a clear baseline is crucial because it allows researchers to assess any changes that occur as a result of the treatment over time. For instance, if a study is investigating the effectiveness of a new drug on blood pressure, the baseline measurements would capture participants' blood pressure levels prior to starting the medication. This ensures that any differences observed post-treatment can be attributed to the intervention rather than other factors.

In contrast, defining a baseline as the first intervention point would not capture the relevant pre-treatment status that is critical for comparison. Similarly, the initial data collected after treatment would not serve as a baseline since it reflects the impact of the treatment rather than the status before it. The idea of calculating the average of all patient responses does not represent the concept of baseline, as it doesn't focus on a specific pre-treatment measurement, instead abstracting data which may not accurately reflect individual changes from baseline.