Sant Joan de Déu Barcelona - Hospital


It is recommended to talk to the doctor so he/she can assess whether someone is suitable to participate in a clinical trial.

In order to obtain information about ongoing clinical trials there are public resources available. In our country, the resource of reference is Registro Español de Estudios Clínicos.

Since 2011, the European Medicines Agency provides a website where all clinical trials carried out in Europe are published:

In the United States of America there is a similar website that includes all clinical trials carried out around the world:

With the purpose of ensuring that clinical trials meet standard ethical requirements, the majority of the studies meet those requirements established in the Declaration of Helsinki, which have additionaly been approved by the World Medical Organization. 

The most important requirement established in the Declaration of Helsinki is the obligation to obtain obtener informed consent before participating in the clinicla trial.

Never. Actually it is usually all the way round. When somebody participates in a clinical trial the medical follow-up is very thorough and medical visits increase, increasing in turn the opportunities to share doubts with the doctor and the options to adquire more information about handling an illness.

It is possibe to have access to the information about the results of a trial once it has been completed. It should be considered that some studies involve thousands of people and that they could last for 5 years or more, exceeding the patient's participation period. 

Thus, there could be a difference of time between the moment when a patient leaves the study and the moment when the clinical trial ends.

Once the trial is finalized, the promoter (this can be a pharmaceutical company or a research centre) should make the results available to the participants. If someone is interested in this information, he could always ask the researcher or the patient's doctor about the conclusions of the trial.

Results should always include information about the benefits and risks of the studied treatments. This information will help the patient and other patients like him/her to make better decisions about healthcare.

Some researchers work with patient groups in order to ensure that the results of the trial reach those patients that have not participated in it. It is compulsory to publish the results of the trial although these have not been positive. This can be done via a medical congress, a scientific journal or the media.

The child can change his/her mind at any time during the running of the clinical trial nd he/she can leave any time he/she wants: before it starts, during the trial or during the follow-up process. Participation in a clinical trial is always voluntary.

Quitting a study will not affect the doctor-patient relation.

A placebo is a substance that has no effect on the patient. It allows researchers to study the “placebo effect”. This is a psychological response in which the patient starts to feel better although he/she has not taken any treatment with an active ingredient in it. 

The comparison between the response of those patients that have taken the treatment and those who have taken the placebo helps researchers to analyze the benefits of the studied treatment.

In these kind of studies both the doctor/researcher and the patient know which treatment is being administered. In other words, we could say that this is an opposite situation to the doule-blinded trials.  

"Exclusion criteria" are those criteria established by the researchers determining that a patient can not participate in a clinical trial. An example would be those studies excluding pregnant women in order to prevent risk of fetus damage.

An exclusion criteria may also be taking any medication that may interact with the studied treatment.

"Inclusion criteria" are characteristics of the patients that help researchers to decide which ones are suitable candidates to participate in a clinical trial. For example, some studies only include patients of a certain age. In other cases it is necessary to perform some medical tests, such as a blood analysis, in order to validate the inclusion of the patient in the study.

Bias are prejudices in favour of or against something, and it makes us wrongly conclude about the effects of a treatment. It is essential to detect any kind of bias in the biomedical research that may induce unsafe or ineficient studies, as well as the suspension of useful treatments.

Researchers try to avoid bias using aleatorization and anonymization (blind), thus obtaining objective assessments in the evaluation of the studies.