Before starting a clinical trial, the type of the trial has to be defined. The type of the trial is part of the selected design of the trial and is determined by the particular research question. Choosing the right type of a clinical trial contributes significantly to the trials‘ success by trying to avoid all influences that could possibly distort the results of the test procedure. The type is decisive for the later evaluation and usability of the collected data. Therefore, a wrong choice can not be corrected once the trial has started.

Types of clinical trials

In clinical trials new drugs or therapies are tested in groups of two or more patients.

Interventional trials vs. observational trials

In the context of clinical trials, a basic distinction is made between interventional trials and observational trials. Interventional trials are intended to show whether or not a certain treatment or drug has an effect on the organism. Observational trials are purely descriptive and involve observing and interviewing the patient, samples are taken if necessary, but no medication or treatment is administered. In addition, clinical trials can be distinguished according to their timing.

Interventional trials 

Interventional trials, (or experimental trials) examine the effect of medical interventions on homogeneous groups of subjects. Intervention means that the patient receives a certain therapy including dose, time of administration and corresponding examinations. Non-interventional, on the other hand, is a therapy determined by the patients‘ physician, whereby the therapy is only observed during the trial. In interventional trials, the medication plan and the entire course of treatment are coordinated in advance, whereas in non-interventional trials the patient simply receives his or her regular therapy.

Interventional trials can be divided into randomised controlled trials and non-randomised controlled trials. In randomised trials, participants are randomly assigned to groups (randomisation).

Here, the verum group is given the actual active substance and the control group receives an alternative active substance or placebo. Thus, a comparison of the treatment results reveals possible differences in the effect of the drug that is to be tested in contrast to other substances or no substances at all.

If a control group exists in addition to the verum group (also called test or intervention group), this is called a controlled trial. The control group receives a placebo (placebo group) or standard therapy (control group). In order to prevent possible falsification of the results, studies are conducted blinded. This means that the participants do not know whether they are in the verum or the control group. A double-blind trial is also possible, in which even the medical staff do not know which patient belongs to which group. If there is no blinding, this is called an open-label trial. In a crossover trial, the intervention and control groups are switched after the first half of the trial.

The randomized controlled trial (RCT) is considered the most suitable type of trial to prove the causality of a mode of action and is, therefore, the best choice for distinct research questions.

Observational trials 

Observational trials can be divided into descriptive and analytical trials. The type of trial depends on the research question.

Descriptive trials 

In descriptive trials, the data collected are therefore documented and evaluated, but no causal relationships are investigated. If the trial addresses questions such as “How common is multiple sclerosis?” or “Which specific laboratory parameters characterise type I diabetes?”, it is a descriptive trial.

Descriptive trials also include, for example, registry trials based on the birth, death or cancer registry.

A cross-sectional trial is a trial that collects clinical findings within a sample at a specific point in time. Cross-sectional trials can therefore be considered as a kind of “snapshots”.

Longitudinal trials, on the other hand, document findings at several times over a longer period of time.

Analytical trials 

Analytical trials explore cause-and-effect patterns such as the relationship between a certain risk factor (exposure) and the occurrence of a disease. For example, the question of an analytical trial could be: “Are smokers more frequently affected by cardiovascular diseases than non-smokers?“

Case-control trials are either retrospective (“looking back”) or prospective (“looking forward”) and compare diseased and healthy patients with regard to different influencing variables. In contrast to cross-sectional studies, statements about cause-and-effect relationships can be made here.

Cohort trials observe participants in a sample selected according to defined characteristics over a longer period of time. Any risk factors (e.g. smoking, working in a mine, etc.) are documented and whether or how frequently certain events (e.g. lung diseases) occur in comparison to non-exposed subjects. If a randomised controlled trial is not feasible for ethical reasons (e.g. a research question on severe cancer or obesity), cohort trials are often conducted.

Pivotal trials 

A pivotal trial is a phase III clinical trial, which is intended to prove the medical efficacy of a drug in contrast to the current therapy standard or a placebo. The data collected in this phase, together with those from the first two phases of a clinical trial, form the basis for the application for approval of a drug.

Case reports and case series 

Case reports document a single case (Case report) or several cases (Case series). Due to the small number of patients, generally valid observations can not be made. Case studies are therefore suitable, for example, for the documentation and reporting of rare adverse events that are not detected in trials.

The Healex Site Management System (SMS)

Multi-site clinical trial management for all types of trials

The Healex Site Management System (SMS) is the leading communication platform for the exchange of information and data between investigators, researchers and sponsors in clinical trials. With the Healex SMS, researchers and physicians can manage trials across all phases. In addition to protocol codes, trial sites, trial objectives, inclusion criteria, or patient characteristics, this includes the design of the trial. Different types of trials and the associated indications and substances, protocols as well as therapy regimen, patient population and trial characteristics can be conveniently entered and managed at a glance.