Depending on the type of study and the stage of drug development, investigators enroll healthy volunteers or patients.
The reliability of the studies is based on a rigorous and proven method to limit any bias or error in data collection and analysis. The Good Clinical Practice Consolidated Guideline is an international standard for bioethics that applies to clinical trials involving human beings.
The following are common aspects of clinical research:
Controlled studies:
A control group is vital to validate the effectiveness of a procedure because it allows the drug’s effects to be compared to a placebo, or lack of treatment.
This control group may be either composed of subjects receiving an inactive treatment or subjects receiving a treatment different to the novel treatment.
The greatest care is taken to form similar groups (age, weight, sex, size, degree of damage, etc.), between the treatment and control group.
Randomized studies:
The assignment of each subject to the treatment group or the control group must be done randomly, hence randomized study.
Blinded studies:
The study is “single-blind” if the subject does not know in which group he or she has been placed (test or control).
The study is “double-blind” when the organizer also does not know which group each subject is in.
The study is “open” if both subject and organizer know to which group the subject has been assigned.
Monocentric and multicentric studies:
While the first phases are generally conducted a single center or clinic, subsequent phases tend to be conducted in multiple countries & centers, to avoid any bias.
Intention-to-treat (ITT) analysis:
All the participants continue to be monitored in the group to which they were assigned, even if they have not fully completed the treatment, to avoid attrition bias, i.e. the “disappearance” of subjects having stopped the treatment for some reason. Since ITT analysis includes all patients regardless of compliance with their assigned treatment, it is considered to be the most conservative analytical method for clinical trials. The alternative is an analysis with only the subjects that completed the study without violating their treatment’s protocol. This is the per-protocol analysis, less conservative than ITT analysis.
The results of a study can be given both in intention-to-treat and per protocol, the first analysis coming closest to reality, the second to ideal conditions.