What are the types of clinical trial?

Clinical trials are essential for the advancement of medicine and healthcare. We can learn more about treating, screening and diagnosing diseases and improving patient outcomes by trialling new drugs, therapies and technologies.

The two main types of clinical trials are interventional and observational–each designed to answer a specific question. Below you’ll find a brief overview of each type.

Interventional trials

Interventional trials involve assigning participants to two or more groups and giving them different treatments, such as a drug, device or procedure. They are designed to control the testing environment to  ensure specific conditions are met during the trial. 

This type of trial is often conducted as a randomised controlled trial (RCT), which is the gold standard for medical research. This means that participants are randomly assigned to receive either a placebo or an active drug or treatment. Randomisation is helpful in reducing the risk of bias that could influence results.

Also called an experimental trial, the goal of this trial is to test the effectiveness of a new intervention against either a placebo (an inactive treatment) or another available intervention (a comparator). These are usually done using blinding methods, such as single-blind or double-blind. But when blinding is not feasible or appropriate, researchers may opt for the open-label type.

Placebo-controlled studies

A placebo-controlled study is an interventional trial in which one group receives the new intervention while another gets a dummy or “placebo” version. This type of trial aims to determine if the new intervention has any effect beyond that of a placebo.

The main benefit of a placebo-controlled study is that it eliminates any potential bias from the participant’s expectation. In addition, because participants in both groups don’t know which treatment they’re receiving, it is easier to compare the results of the different treatments and draw accurate conclusions about their efficacy.

Comparator studies

Comparator studies are also interventional trials but do not involve a placebo. Instead,  participants receive a drug/treatment already  available available on the market, that is expected to produce similar outcomes.

The main benefit of a comparator study is that it allows researchers to compare two or more interventions side-by-side and draw conclusions about their relative safety and efficacy.

Open-label studies

Usually, interventional trials use either a single-blind or double-blind approach. In single-blind studies, only the researchers know which participants receive which treatments while the participants do not. In double-blind studies, neither the researchers nor the participants know who is receiving what treatment.

An open-label study is different because it does not use this type of blinding. Both the researchers and the participants know which treatment each participant is receiving. According to the book Principles and Practice of Clinical Trial Medicine, researchers opt for this type of trial if “blinding is neither feasible nor ethical or in cases where the outcome is completely objective, such as survival.”

Observational trials

Unlike interventional trials, observational studies do not involve assigning participants to different groups. Instead, they observe existing patients in real-world settings.

Observational studies can provide valuable insights into the long-term effects of a given intervention and any potential adverse effects. They also allow researchers to look into rare events or conditions that wouldn’t be feasible to study in a clinical trial setting.

The main benefit of observational trials is that they provide a more realistic assessment of the risks and benefits associated with an intervention. Experimental trials are often conducted in controlled settings, which may not reflect how the intervention will be used in real-world clinical practice.

Clinical trials in drug, therapy and technology research

Clinical trials are not exclusive to drug research; they can also be used to test new therapies and technologies. Below are some examples of these.

Gene therapy

Gene therapy is an experimental technique that uses genes to treat or prevent disease. The SPR1NT trial is an example. It’s currently testing a new gene therapy for Spinal Muscular Atrophy (SMA), a rare and debilitating illness. If untreated, children with SMA won’t live more than 12 months.

So far, the results of the trial have been promising. An update from the Australian Trade and Investment Commission reported that patients who received the SMN gene are all “alive and do not need breathing or feeding support.”

Bionic ear

A bionic ear, or cochlear implant, is a device that can be surgically implanted in the ear to help people with hearing loss. Before this device, deaf people relied on hearing aids and other external devices to communicate.

Through the efforts of the National Health and Medical Research Council, the University of Melbourne and Nucleus Ltd, clinical trials began for the device in 1982. Four decades later, cochlear implantation has become a standard treatment option for hearing loss and is used globally.


Charco Neurotech’s CUE1 is a wearable device designed to improve the mobility of people with Parkinson’s Disease (PD). PD is a neurological disorder that affects movement, balance, and coordination.

Clinical trials for the CUE1 device are underway in England and have seen some early positive results. Based on the latest user testing report, participants in the trial have reported improved mobility, ranging from 4.96 per cent up to 32.38 per cent.


No matter what intervention is being tested, clinical trials are essential to ensure that any new treatments or technologies are safe and effective before they are widely used.

If you want to get involved in clinical trials, you can find more information by visiting our blog page. At White Coats Foundation, we want to help you become informed about clinical trials and how research affects consumers and communities. In addition, we provide credible resources so you can feel confident while making decisions along your journey.

Please note that this discussion only serves as a broad overview of various types available today. With the continued evolution of modern science, clinical trial types and designs are advancing and becoming more sophisticated

White Coats Foundation 

White Coats is a Not for Profit Australian-based charity.  The Foundation was established in recognition of the need to raise awareness about the role of clinical trials in advancing medical science and healthcare. We are providing information about clinical trials through our Webinar Series and Our Blogs.

At White Coats Foundation, we provide access to credible resources and information to help guide people’s journey in understanding clinical trials and consumer and community involvement in research.

Please note: White Coats blogs are informational only and do not constitute advice. Please contact your relevant healthcare professional for advice on clinical trials for you.

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