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Why is it important that groups are similar at baseline in an intervention study?
If randomisation is successful and the groups are similar at baseline, the investigator can be more confident that observed differences in outcomes between the groups are related to the intervention rather than confounding factors.
What is a baseline difference?
Meaningful differences here refer to differences in baseline characteristics that influence (confound) the results of a trial. In other words, confounding occurs when there is a difference between the intervention and control groups in a certain characteristic that is prognostic for the outcome of that trial.
Is there a problem with group imbalance at baseline?
However, imbalance between groups in baseline variables that may influence outcome (such as age or disease severity) can bias statistical tests, a property sometimes referred to as chance bias.
What are baseline imbalances?
A term of art for a systematic error in creating intervention groups in a clinical trial, such that participants differ with respect to prognosis—i.e., the groups differ in baseline characteristics because of the way in which the participants were selected or assigned—or because the participants are not representative …
What can we learn from baseline characteristics?
Baseline characteristics also allow the success of randomisation to be assessed. In studies where important baseline factors appear well balanced, it is likely that any differences in outcome between the intervention and control groups are a real effect of treatment (one component of internal validity).
What is a baseline variable?
A baseline covariate is usually defined as a qualitative factor or a quantitative variable measured or observed before a subject starts taking study medication (usually before randomisation) and expected to influence the primary variable to be analysed.
What are baseline characteristics?
Baseline characteristics or data are demographic, medical and other information, particularly prognostic variables. Researchers collect this information about each participant at the beginning of a study, before they have received the treatments that are going to be compared in a treatment comparison.
What is baseline Characteristics Table?
Generally, a table with baseline characteristics is provided, where investigators report demographic and pertinent clinical variables based on the random group assignment and P values for the each variable in attempt to either support the balanced assignment or to indicate that the balance between groups was not ideal.
How many participants are in a RCT?
Parallel RCT design is most commonly used, which means all participants are randomized to two (the most common) or more arms of different interventions treated concurrently.