What Are Randomized Controlled Trials?

Clinical trials come in many different forms and sizes, and randomized controlled trials (RCTs) are just one type of clinical trial you might come across. RCTs serve as a key research tool in medical science, enabling researchers to test hypotheses in a controlled environment on a randomized basis. The randomization element ensures the data produced is highly reliable and results from the trial elements only.

What is a randomized controlled trial (RCT)?

A randomized controlled trial is a research methodology commonly used in healthcare research. It is designed to evaluate the efficacy and safety of various medical interventions, from new drugs to alternative treatments. In an RCT, participants are randomly assigned to either a treatment or control group, which is what makes this type of trial different from others.

By assigning participants randomly, researchers can be confident that any differences observed between the groups during the trial are down to the intervention itself, as opposed to other external or internal factors.

Randomized vs non-randomized controlled trials

The key difference between randomized controlled trials and non-randomized controlled trials is the randomization element. In RCTs, a random process is used to assign treatments which ensures the unbiased distribution of participants across the groups. The opposite is true in non-randomized controlled trials, whereby the allocation of treatments could be influenced by selection bias.

Additionally, the random selection of participants can help deliver a more diverse participant pool, which enhances the generalizability of the study findings to a broader population after approval.

The outcomes of both types of trials can be different too. While RCTs help researchers more confidently establish any causality between interventions, the design of non-randomized controlled trials makes this more difficult.

Key elements of randomized controlled trials

Like other trials, randomized controlled trials are designed with several key elements, each playing a vital role in minimizing bias and providing reliable results. RCT foundational elements include randomization, control groups, blinding/masking, and placebo control. Ensuring each of these elements is included in the planning of a randomized clinical trial helps to ensure it is effective and offers scientific validity.

Randomization

As the main element and differentiator with randomized controlled trials, randomization is vital for ensuring each participant has an equal chance of being assigned to any of the study groups. As a result of using randomization in clinical trials, selection bias is minimized and researchers can have more confidence in their data.

Control group vs. experimental group

After participants are randomized, they will be assigned to either a control or experimental group. The control group participants will not receive the new drug or treatment, and will instead receive either a placebo or an existing standard treatment. This helps to provide a baseline for comparison. The experimental group will receive the new treatment being studied, enabling researchers to evaluate its effectiveness.

Blinding or masking

With blinding, also known as masking, participants, researchers, or both are not aware of which group participants are assigned to. This method helps to deliver true randomization and further ensures selection bias is reduced. There are several types researchers can use, including single blinding, double blinding, and triple blinding. The type chosen for a study will depend on who is being blinded.

Placebo control

Randomized controlled trials often use placebos in the control group to help establish the effects of the treatment. Researchers can better measure the treatment’s effect by distinguishing it from any effects not attributable to the treatment itself. A placebo is an inactive treatment that offers the same look, feel, and taste as the real treatment, but it has no therapeutic effect.

Importance of randomized controlled trials in research and medicine

Randomized controlled trials are considered to be the highest standard for generating dependable and objective data in medical research. Minimizing bias and confounding variables via randomized design makes RCTs highly important in medical research, enabling researchers to isolate the effects of an intervention and test hypotheses more effectively.

Reduction of bias

Reducing bias in clinical trials is of the utmost importance, and the structured controls of randomized controlled trials make this possible. With controls such as blinding and placebos regular features of RCTs, researchers can maintain the integrity of a study by preventing results from being impacted or skewed by participants’ or researchers’ expectations.

By using these methods in RCTs, researchers can have more confidence that the measured outcomes are directly attributable to the intervention and not external influences.

Enhancing reliability

RCTs are known as the gold standard in clinical research due to the reliability of data gathered. This is possible thanks to the rigorous methodologies used by researchers in these studies, including standard protocols and statistical analyses. With more reliable data, findings of RCTs are more consistent and can be replicated in subsequent studies. This supports the accumulation of scientific knowledge, helping to advance medical practice and support medical professionals in making informed decisions.

Supporting evidence-based practice

With reliable and scientifically validated results, RCTs are commonly used to inform healthcare policies and establish clinical guidelines. Patient care can then be based on the most effective and safe treatments available, promoting the best possible outcomes for patients.

Positive impact on patient care

Like any clinical study, patient care is the number one priority. Randomized controlled trials consistently have a positive impact on patient care by reliably and more accurately testing the efficacy and safety of new treatments. Using the results, researchers can confirm whether new treatments perform better than existing treatments or placebos, leading to improved healthcare outcomes for all.

Disadvantages and limitations of randomized controlled trials

While randomized controlled trials have a multitude of benefits, every trial type has some drawbacks too. RCTs often face significant challenges and limitations that can affect the implementation and interpretation of results.

High-cost and resource intensive

With more protocols in place than some other types of clinical study, RCTs often come with higher costs and a need for more resources. The setup, monitoring, and administration of randomized controlled trials require a large amount of financial investment. This is usually down to the requirement for specialized staff, equipment, and facilities.

Human resources are a huge cost for RCTs. These trials need people to design the study, recruit participants, manage data, and maintain regulatory compliance, leading to large numbers of staff being required. Sometimes, this can result in resources being taken away from other research or clinical activities, which could impact the effectiveness of other studies.

Participant compliance

Participants in a clinical study are the most unpredictable element, and this is also true in randomized controlled trials. It can be difficult to ensure participants adhere to the treatment protocols, especially in long-term studies as the risk of non-compliance inevitably increases.

The problem with non-compliance is that it can result in high drop-out rates, compromising the validity of the study results. This means the final sample may not be representative of the original group, resulting in less valid results than initially thought.

Slow to adapt to new findings or insights

Randomized controlled trials can vary in length, which means new findings or insights could be released while the study is underway. Due to the way RCTs are set up, it can be logistically and bureaucratically difficult to alter protocols in response to these new findings or techniques. Randomized controlled trials traditionally don’t lend themselves well to dynamic adaptation to evolving scientific insights, potentially leading to outdated or less relevant results by the time the trial is finished.

Ethical dilemmas

Ethics is a hot topic in clinical trials, and the use of placebos in some randomized controlled trials can raise additional ethical concerns. Using placebos, particularly when effective treatments are available, can cause concerns about the denial of potentially life-saving treatments for participants.

Researchers need to balance scientific rigor with the ethical requirement to provide the best-known medical care for all participants. In RCTs, this is difficult and can often lead to conflicts between researchers and ethics review boards, as well as participants.

Examples of randomized clinical trials

Throughout history, there have been some excellent examples of randomized clinical trials. With many being so successful and contributing to scientific knowledge, it’s clear to see why randomized controlled trials are considered to be the highest standard of clinical trials. The following trial examples are not just renowned for their findings, but for the wider impacts they had on health guidelines and patient care practices around the world.

The British Doctors Study (1951 - 2001)

In 1951, a randomized study began to establish the effects of smoking. This landmark RCT was conducted by Richard Doll and Austin Bradford Hill, who sought to establish a link between tobacco smoking and cause-specific mortality including lung cancer and heart disease. This was one of the first major studies using the RCT design to establish robust epidemiological data. The results of this study, particularly the 10, 20, 40 and 50-year results, have significantly impacted personal decisions about quitting smoking.

The Women’s Health Initiative (1991)

After menopause, the most common diseases affecting women are cardiovascular disease, breast cancer, colorectal cancer, and osteoporosis. In 1991, the National Heart, Lung and Blood Institute launched the Women’s Health Initiative to better understand how these diseases affect post-menopausal women and how the number of women who develop and die from them could be reduced. Over 160,000 post-menopausal women participated in the randomized study over 15 years, making it one of the biggest prevention studies involving women in the US.

The study tested the effects of hormone replacement therapy, dietary modifications, and calcium and vitamin D supplements on health outcomes. The results published in 2002 found that women taking combination hormone therapy had an increased risk for some conditions. The study resulted in a sharp decline in breast cancer in 2003.

Participating in a randomized controlled trial

Participation in a randomized controlled trial has many benefits, including helping to validate new medical treatments and enhance scientific understanding in the development of new treatments. Furthermore, you can gain an insight into how medical research is conducted and how treatments are systematically tested for efficacy and safety. By participating, you will also feel a sense of pride in your contribution to medical treatments of the future.

Active clinical trials

Whether you’re simply curious to learn how clinical trials work, or you’re actively seeking to participate in a clinical trial, there are many ways to find suitable clinical trials for your needs. You can browse active clinical trials in our wide database, or speak to your healthcare provider for more information about ongoing trials in your area.

Conclusion

Randomized controlled trials are vital in validating the efficacy and safety of new treatments and drugs. The design of this type of study provides a highly reliable basis for medical practice and patient care, ensuring healthcare decisions can be informed by the strongest scientific evidence. Although there are challenges with this type of study, RCTs are still the cornerstone of evidence-based medicine, and continue to evolve with advancements in technology and methodology.