Question
Asked 3rd Aug, 2016

What is the difference between an end-point and an outcome measure?

In a clinical study, what is the difference between an end-point and an outcome measure?
Are they synonyms?

Most recent answer

30th Nov, 2020
Andrius Vagoras
Vilnius University
I like this explanation...
" For an explanatory trial, investigators can specify any outcome or endpoint, define the endpoint, and then measure it. The term outcome usually refers to the measured variable (eg, peak volume of oxygen or PROMIS Fatigue score), whereas an endpoint refers to the analyzed parameter (eg, change from baseline at 6 weeks in mean PROMIS Fatigue score). Even after a specific outcome is selected, it may be challenging to determine the best way to measure the effect of an intervention in terms of an analyzable endpoint, especially with pragmatic research where data are collected as part of routine care.
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Popular Answers (1)

3rd Aug, 2016
Ilya B. Tsyrlov
XENOTOX Inc., USA
Hi Kanchan,
There is a delicate equilibrium between an endpoint and an outcome measure, rather than a simple alternative: difference vs synonyms. Just look through basis several clinical circumstances surrounding these terms, in their application to each individual clinical situation.
1)     “Direct” Endpoints. Clinically meaningful endpoints that directly measure how a patient feels, functions, or survives • Endpoints that in themselves represent or characterize the clinical outcome of interest – Objective: survival, disease exacerbation, clinical event (e.g. MI, stroke), etc. – Subjective: symptom score, “health related quality of life” (validated instrument), etc.
2)     Surrogate Endpoints • A surrogate endpoint is a laboratory measure or a physical sign that is intended to be used as a substitute for a clinically meaningful endpoint. • Ideally, the surrogate should exist within the therapeutic pathway between the drug and meaningful benefit – i.e. the drug results in the therapeutic benefit by virtue of its effect on the surrogate • Changes induced by a therapy on a surrogate endpoint are expected to reflect changes in a clinically meaningful endpoint.
3)     Composite Endpoints • A single measure of effect, based on a combination of individual endpoints. • Particularly useful for drugs that can benefit patients in several ways or if component events are infrequent. • Examples: – Cardiovascular death or hospitalization for heart failure – “MACE” (major adverse cardiac events): cardiovascular death, non-fatal MI, and non-fatal stroke – “Clinical Worsening” : may include categorical decline in functioning, worsening symptoms, addition of a new medication, hospitalization due to the disease, death, etc. – (HRQOL instruments) • Often analyzed as time to first event, or number of events over the study period.
Considerations: – So, each component should itself be clinically meaningful. – Ideally, each component would be approximately equally meaningful. – “Success” should not be concluded if driven by a less meaningful component, if there is evidence of a therapeutic disadvantage on a more meaningful component. – The composite should not include individual components for which a treatment effect is not expected. – May complicate communication of the established benefit of a drug. • There may often be inadequate evidence to establish a treatment effect on any of the components individually.
4)     As for Patient Reported Outcomes, any report of the status of the patient’s health that comes directly from the patient, without interpretation of the patient’s response by a clinician or anyone else. – e.g. symptoms, functioning, or a more global assessment of the effect of the disease on health and functioning from the patient’s perspective (“health related quality of life”) • Intuitively desirable. A very reasonable goal of therapy would be to make the patient feel better in some way. Sometimes the benefit of a drug may only be detected or described by the patient. • Current standards for PRO instrument development, validation, and application in clinical trials reflect increasing sophistication in the field.
Best wishes,
Ilya
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All Answers (11)

3rd Aug, 2016
Ilya B. Tsyrlov
XENOTOX Inc., USA
Hi Kanchan,
There is a delicate equilibrium between an endpoint and an outcome measure, rather than a simple alternative: difference vs synonyms. Just look through basis several clinical circumstances surrounding these terms, in their application to each individual clinical situation.
1)     “Direct” Endpoints. Clinically meaningful endpoints that directly measure how a patient feels, functions, or survives • Endpoints that in themselves represent or characterize the clinical outcome of interest – Objective: survival, disease exacerbation, clinical event (e.g. MI, stroke), etc. – Subjective: symptom score, “health related quality of life” (validated instrument), etc.
2)     Surrogate Endpoints • A surrogate endpoint is a laboratory measure or a physical sign that is intended to be used as a substitute for a clinically meaningful endpoint. • Ideally, the surrogate should exist within the therapeutic pathway between the drug and meaningful benefit – i.e. the drug results in the therapeutic benefit by virtue of its effect on the surrogate • Changes induced by a therapy on a surrogate endpoint are expected to reflect changes in a clinically meaningful endpoint.
3)     Composite Endpoints • A single measure of effect, based on a combination of individual endpoints. • Particularly useful for drugs that can benefit patients in several ways or if component events are infrequent. • Examples: – Cardiovascular death or hospitalization for heart failure – “MACE” (major adverse cardiac events): cardiovascular death, non-fatal MI, and non-fatal stroke – “Clinical Worsening” : may include categorical decline in functioning, worsening symptoms, addition of a new medication, hospitalization due to the disease, death, etc. – (HRQOL instruments) • Often analyzed as time to first event, or number of events over the study period.
Considerations: – So, each component should itself be clinically meaningful. – Ideally, each component would be approximately equally meaningful. – “Success” should not be concluded if driven by a less meaningful component, if there is evidence of a therapeutic disadvantage on a more meaningful component. – The composite should not include individual components for which a treatment effect is not expected. – May complicate communication of the established benefit of a drug. • There may often be inadequate evidence to establish a treatment effect on any of the components individually.
4)     As for Patient Reported Outcomes, any report of the status of the patient’s health that comes directly from the patient, without interpretation of the patient’s response by a clinician or anyone else. – e.g. symptoms, functioning, or a more global assessment of the effect of the disease on health and functioning from the patient’s perspective (“health related quality of life”) • Intuitively desirable. A very reasonable goal of therapy would be to make the patient feel better in some way. Sometimes the benefit of a drug may only be detected or described by the patient. • Current standards for PRO instrument development, validation, and application in clinical trials reflect increasing sophistication in the field.
Best wishes,
Ilya
9 Recommendations
3rd Aug, 2016
Kanchan Batra
King's College London
Thank you so very much Ilya for your prompt and detailed response. Much appreciated.
1 Recommendation
22nd Aug, 2016
Urszula Kosecka
Humber College
Hello Kanchan, 
Ilya has provided very good explanation. I may add that in clinical trials some companies use expression  "outcome trials"; this expression is used for major, crucial phase III studies. 
Thank you
Urszula
4 Recommendations
13th Nov, 2016
Kanchan Batra
King's College London
Many thanks Urszula....that is really helpful to know.
Kind regards, Kanchan
2nd Mar, 2019
Desta Kassa
Ethiopian Health and Nutrition Research Institute
Thank you so much
12th Oct, 2019
Mario A Svirsky
New York University
There have been great, detailed explanations before but I would like to add a quick comment.
In the United State, the National Cancer Institute of NIH defines clinical trial endpoints as "an event or outcome that can be measured objectively to determine whether the intervention being studied is beneficial". For example, an endpoint might be improvement in quality of life using a particular index or instrument, or the percentage of patients who show at least a certain amount of improvement using the same index. In this case the quality of life index is typically called an outcome measure and the two examples listed above are examples of endpoints based on that particular outcome measure.
2 Recommendations
13th Feb, 2020
Bev Miller
Temple University
Yes, they are synonyms of each other.
18th Jun, 2020
Philip M Jones
The University of Western Ontario
In the medical research world, the gold standard reporting guidelines from the Equator network use the term 'outcome' ubiquitously. I don't think they use the word 'endpoint' at all. I personally use outcome as well. 'Endpoint' is an awkward, non-descriptive word. Outcome is understood by everyone.
1 Recommendation
20th Jun, 2020
Kanchan Batra
King's College London
Thank you
17th Sep, 2020
Asghar Mohamadi
Lorestan University of Medical Sciences
It's very valuable comment

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