Definition Of Surrogate Endpoint

Surrogate endpoints, also known as surrogate indicators, serve as substitute guides for checking on the total health of a patient in a medical trial. While clinical endpoints give exact data relating to overall health and the efficacy of a treatment, surrogate endpoints can serve as stand-ins, providing needed information that correlates with possible diseases and complications. Surrogate endpoints allow treatment options to be planned in advance of more dire symptoms.

Definition of Surrogate Endpoint

• "Bandolier," an independent journal written by Oxford professors, defines a surrogate endpoint as "outcome measures that are not of direct practical importance, but are believed to reflect outcomes that are important." In other words, surrogate endpoints are not the items being measured directly, but other items that may correlate with a clinical endpoint that is the direct focus of a medical study. Surrogate endpoints are usually less life-threatening than clinical endpoints.

Definition of Clinical Endpoint

• A clinical endpoint is a marker that can be directly measured and correlated to a certain treatment. For instance, the British Medical Journal provides the example of a five-year survival. If any patient survives five years, she can be said to have reached the "clinical endpoint" of the study. Thus, for the purposes of the study, she would be released from further scrutiny or changes in treatment.

Examples

• One of the most common surrogate endpoints is blood pressure. While not important in and of itself, blood pressure is often used as an indicator of poor cardiac health and the risk of heart attack. In this situation, having a heart attack would be the clinical endpoint; the blood pressure that indicated an increased probability of the clinical indicator is the surrogate indicator.

Uses

• Surrogate endpoints are often used to quickly document the usefulness of a treatment. They are also used to diagnose potential health concerns in individuals. Further, in clinical trials in which the clinical endpoints are difficult to measure due to inaccurate testing methods or the length of the study (many running for several years), surrogate endpoints can provide early data that can guide future research and study.

Controversies

• Some question the usefulness of surrogate endpoint studies because the existence of a surrogate endpoint indicates but does not guarantee an expected clinical endpoint. Thus, this has led to questions about a number of drugs, particularly in regards to cholesterol reduction and its overall benefit in heart health. Supporters of surrogate endpoint studies point to the oppressive length of clinical endpoint studies and the larger study sizes of surrogate endpoint studies to demonstrate their usefulness in studying new drugs and their effectiveness.