Comparator Products:  Hart’s Good Clinical Practice glossary series

Welcome back!  This is the Hart GCP knowledge series where we are reviewing key definitions found in the Good Clinical Practice (GCP)  guidelines.  In this entry, we are looking at the term Comparator Product.

The guideline defines a comparator product as “An investigational or marketed product (i.e., active control), or placebo, used as a reference in a clinical trial.”  Now, this is not an exceptionally thorough definition, so we’ll dive a little deeper.

The FDA also references the ICH GCP Guidance for Industry E10 – Choice of Control Group and Related Issues in Clinical. This document, last updated in 2001, describes control groups in various clinical study designs. It is intended to assist sponsors in choosing a control group for clinical studies that are evaluating efficacy.


It says that the main purpose of a comparator product is “to allow discrimination of patient outcomes (for example, changes in symptoms, signs, or other morbidity) caused by the test treatment from outcomes caused by other factors, such as the natural progression of the disease, observer or patient expectations, or other treatment.” In other words,

“The control group experience tells us what would have happened to patients if they had not received the test treatment or if they had received a different treatment known to be effective.”


The guidance goes on to describe different trial design elements, such as randomization and blinding. It also describes different types of concurrent controls like placebo, no-treatment, dose-response, and active types.  Finally it describes external, historical, and multiple group controls.  For each of these types of study design elements and controls, the guidance provides details for its use:

  • Its ability to minimize bias
  • Ethical and practical issues associated with its use
  • Its usefulness and the quality of inference in particular situations
  • Modifications of study design or combinations with other controls that can resolve ethical, practical, or inferential concerns
  • Its overall advantages and disadvantages

If you aren’t familiar with this guidance document, we encourage you to look here for more information before you design your next study.

Thank you for reading HCC’s glossary series!

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