Basic↦Statistic Methodology↦Research Question↦Study Outcome Endpoint
What is it? Why is it important?
Study outcomes/endpoints are variables measured during the conduct of a study in order to answer (a) research question(s).
One differentiates between:
- A primary Outcome/Endpoint: considered the most important variable to researchers, as it is expected to answer the main study question (e.g. the primary outcome of a study assessing the effect of a new diabetic medication would be the blood glucose concentration)
- Secondary Outcomes/Endpoints: are additional variables monitored during study conduct with the aim to support the interpretation of the primary outcome/endpoint (e.g. in the diabetic study this could be the occurrence of adverse events, ease of drug administration by patients including compliance)
- Safety Outcomes/Endpoints: are adverse events or negative effects experienced by participants during the course of a study. These outcomes are crucial to evaluate the safety and tolerability of a medical intervention
- Other Outcomes/Endpoints of interest: include measurements researchers believe to be informative, but which do not neatly fit the classifications
More
In an intervention study, outcomes/endpoints document the potential health effect of a given intervention within a population.
Safety outcomes can include a wide range of effects, from mild discomfort or side effects to severe complications or even death. Common safety outcomes assessed in clinical studies may notably include Adverse events (AEs), Serious adverse events (SAEs), Adverse drug reactions (ADRs).
What do I need to do?
As a SP-INV:
- Carefully define the outcomes/endpoints of your study. Their definitions should occur early during study planning, preferably during the concept phase of your study (e.g. at the time when selecting your study design).
- Based on your primary outcome/endpoint, perform the sample size calculation of your study (i.e. an estimation of the required number of study participants needed to answer your study question)
- Together with a statistician, describe the methodology that will be used to analyse the outcome(s) / endpoint(s)
Typically, studies only have one primary outcome/endpoint. However, multiple primary outcomes/endpoints may be specified when it is not possible to use a single outcome to fully assess the effect of an intervention.
Example: in a study assessing the effect of an anti-hypertensive drug, both a change in blood pressure and the occurrence of cardiovascular events may be important primary outcomes.
Where can I get help?
Your local CTU↧ can support you with experienced staff regarding this topic
Basel, Departement Klinische Forschung, CTU, dkf.unibas.ch
Lugano, Clinical Trials Unit, CTU-EOC, www.ctueoc.ch
Bern, Clinical Trials Unit, CTU, www.ctu.unibe.ch
Geneva, Clinical Research Center, CRC, crc.hug.ch
Lausanne, Clinical Research Center, CRC, www.chuv.ch
St. Gallen, Clinical Trials Unit, CTU, www.kssg.ch
Zürich, Clinical Trials Center, CTC, www.usz.ch
References
ICH Topic E9 statistical Principles for Clinical Trials – see in particular
- 2.2.2 Primary and secondary variables
- 2.2.4 Global assessment variables
- 2.2.5 Multiple Primary Variables
Swiss Law
ClinO – see in particular article
- Art. 2b Definition of intervention