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More information, about clinical center, clinical trials and you, participate in a study, referring a patient, about clinical research.

Research participants are partners in discovery at the NIH Clinical Center, the largest research hospital in America. Clinical research is medical research involving people The Clinical Center provides hope through pioneering clinical research to improve human health. We rapidly translate scientific observations and laboratory discoveries into new ways to diagnose, treat and prevent disease. More than 500,000 people from around the world have participated in clinical research since the hospital opened in 1953. We do not charge patients for participation and treatment in clinical studies at NIH. In certain emergency circumstances, you may qualify for help with travel and other expenses Read more , to see if clinical studies are for you.

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The National Institutes of Health (NIH) Clinical Center Search the Studies site is a registry of publicly supported clinical studies conducted mostly in Bethesda, MD.

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Why Do Researchers Do Different Kinds of Clinical Studies?

Clinical research is the study of health and illness in people.

Scientists may have many reasons for doing a clinical study, such as:

• To explore the cause of a disease or a set of symptoms
• To test if a treatment will help with a symptom or condition
• To learn how a certain behavior affects people’s health

Different types of clinical studies are used in different circumstances. Depending on what is known and what isn’t, scientists may even study the same research question using different kinds of studies and in different groups of people. Here are different types of clinical studies and why they might be used.

Observational Studies

In many studies, researchers do not do experiments or test new treatments; they observe. Observational studies help researchers understand a situation and come up with hypotheses that can be put to the test in clinical trials.

Observational studies can find associations between things but can’t prove that one thing causes another. Types include:

Case Study/Case Series

A detailed description of one or more patients. By documenting new and unusual cases, researchers start to generate hypotheses about causes or risk factors.

• Epidemiological Study

Compares the rate of a disease or condition for groups of people, such as towns in different climates or with different average incomes.

• Cross-Sectional Study

A snapshot of many people at one moment in time. These studies can show how common a condition is and help identify factors associated with it.

Case-Control Study

A group of people who have a condition is compared to a control group of people who don’t. Possible causes or risk factors can emerge.

Cohort Study

A large group of people is observed over time. Some eventually develop a disease or condition. Researchers can learn how often the condition occurs and find possible causes or risk factors.

Clinical Trials

In these studies, researchers test new ways to prevent, detect, or treat disease. Treatments might be new drugs or combinations of drugs, new surgical procedures or devices, or new ways to use existing treatments. Clinical trials can also test other aspects of care, such as ways to improve the quality of life for people with chronic illnesses.

A well-designed clinical trial is the gold standard for proving that a treatment or medical approach works, but clinical trials can’t always be used. For example,

scientists can’t randomly assign people to live in different places, or ask people to start smoking or eating an unhealthy diet. Clinical trials are conducted in phases:

• Purpose: Find out whether a medical approach (e.g., drug, diagnostic test, device) is safe, identify side effects, and figure out appropriate doses.
• Number of people: Typically, fewer than 100
• Purpose: Start testing whether a medical approach works. Continue monitoring for side effects; get information that goes into designing a large, phase III trial.
• Number of people: Typically, 100-300
• Purpose: Prove whether a medical approach works; continue monitoring side effects.
• Number of people: As many as needed or able to enroll—can be 1,000 or more
• Purpose: When a medical approach is being marketed, continue gathering information on its effects.
• Number of people: Thousands

How good are these kinds of studies at showing cause and effect?

The strength of a study depends on its size and design. New results may confirm earlier findings, contradict them, or add new aspects to scientists’ understanding. In the end, cause and effect are usually hard to establish without a well-designed clinical trial.

Least Effective to Most Effective:

• Case-Control Study/Cohort Study
• Case Study/Series
• Clinical Trial

What can I do to help?

You’ve begun! Learning about what results mean will help you make good choices with your health care provider.

You could also consider volunteering either as a healthy volunteer or as a participant who has a particular disease or condition.

For more information about clinical trials:

ClinicalResearchTrials.nih.gov

[email protected]

Produced by the National Institutes of Health, the largest source of public funding for medical research in the world. NIH’s mission is to seek fundamental knowledge about the nature and behavior of living systems and the application of that knowledge to enhance health, lengthen life, and reduce illness and disability.

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Science, health, and public trust.

September 8, 2021

Explaining How Research Works

We’ve heard “follow the science” a lot during the pandemic. But it seems science has taken us on a long and winding road filled with twists and turns, even changing directions at times. That’s led some people to feel they can’t trust science. But when what we know changes, it often means science is working.

Explaining the scientific process may be one way that science communicators can help maintain public trust in science. Placing research in the bigger context of its field and where it fits into the scientific process can help people better understand and interpret new findings as they emerge. A single study usually uncovers only a piece of a larger puzzle.

Questions about how the world works are often investigated on many different levels. For example, scientists can look at the different atoms in a molecule, cells in a tissue, or how different tissues or systems affect each other. Researchers often must choose one or a finite number of ways to investigate a question. It can take many different studies using different approaches to start piecing the whole picture together.

Sometimes it might seem like research results contradict each other. But often, studies are just looking at different aspects of the same problem. Researchers can also investigate a question using different techniques or timeframes. That may lead them to arrive at different conclusions from the same data.

Using the data available at the time of their study, scientists develop different explanations, or models. New information may mean that a novel model needs to be developed to account for it. The models that prevail are those that can withstand the test of time and incorporate new information. Science is a constantly evolving and self-correcting process.

Scientists gain more confidence about a model through the scientific process. They replicate each other’s work. They present at conferences. And papers undergo peer review, in which experts in the field review the work before it can be published in scientific journals. This helps ensure that the study is up to current scientific standards and maintains a level of integrity. Peer reviewers may find problems with the experiments or think different experiments are needed to justify the conclusions. They might even offer new ways to interpret the data.

It’s important for science communicators to consider which stage a study is at in the scientific process when deciding whether to cover it. Some studies are posted on preprint servers for other scientists to start weighing in on and haven’t yet been fully vetted. Results that haven't yet been subjected to scientific scrutiny should be reported on with care and context to avoid confusion or frustration from readers.

We’ve developed a one-page guide, "How Research Works: Understanding the Process of Science" to help communicators put the process of science into perspective. We hope it can serve as a useful resource to help explain why science changes—and why it’s important to expect that change. Please take a look and share your thoughts with us by sending an email to  [email protected].

Below are some additional resources:

• Discoveries in Basic Science: A Perfectly Imperfect Process
• When Clinical Research Is in the News
• What is Basic Science and Why is it Important?
• ​ What is a Research Organism?
• What Are Clinical Trials and Studies?
• Basic Research – Digital Media Kit
• Decoding Science: How Does Science Know What It Knows? (NAS)
• Can Science Help People Make Decisions ? (NAS)

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The State of the U.S. Biomedical and Health Research Enterprise

National Academy of Medicine; The Learning Health System Series ; Editors: Shannon Takala-Harrison , Audrey M. Huang , and Melissa H. Laitner .

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The U.S. biomedical research enterprise has played a vital role in advancing science, human health, and the economy. It has contributed significantly to fields such as agriculture, environmental remediation, job creation, and technological innovation. Over the past 80 years, landmark achievements include reducing cancer mortality, developing HIV/AIDS treatments, sequencing the human genome, and creating vaccines that mitigated the impact of the COVID-19 pandemic. The enterprise has grown remarkably in less than a century and holds even greater potential for future success. However, its progress is hindered by a lack of high-level national coordination, a fragmented funding system, and a declining workforce.

The State of the U.S. Biomedical and Health Research Enterprise: Strategies for Achieving a Healthier America addresses these challenges in five key areas-strategic vision, funding, health equity, coordination and convergence science, and workforce development-offering a roadmap that could be used to sustain U.S. leadership in global health.

• Collapse All
• LEADERSHIP INNOVATION IMPACT for a healthier future
• ABOUT THE NATIONAL ACADEMY OF MEDICINE
• THE STATE OF THE U.S. BIOMEDICAL AND HEALTH RESEARCH ENTERPRISE
• CONSULTATIVE EXPERTS
• ACRONYMS AND ABBREVIATIONS
• AUTHOR GROUP
• APPROACH AND METHODOLOGY
• PRIORITIES FOR A RENEWED AND REVITALIZED U.S. BIOMEDICAL RESEARCH ENTERPRISE
• THE IMPACT OF THE U.S. BIOMEDICAL RESEARCH ENTERPRISE
• HISTORY AND CURRENT STATE OF THE U.S. BIOMEDICAL RESEARCH ENTERPRISE
• THE U.S. BIOMEDICAL RESEARCH ENTERPRISE IS AN ENGINE FOR THE U.S. ECONOMY
• WHY DOES THE U.S. BIOMEDICAL RESEARCH ENTERPRISE NEED ATTENTION IN 2024?
• VISION FOR THE U.S. BIOMEDICAL RESEARCH ENTERPRISE OF THE FUTURE
• Vision for the Future
• FRAGMENTATION STANDS IN THE WAY OF MAXIMUM POTENTIAL
• THE ROLE OF NIH
• WHY A NATIONAL STRATEGIC VISION IS NECESSARY
• PUBLIC TRUST IS CRITICAL FOR THE ACCEPTANCE OF A NATIONAL STRATEGIC VISION
• MORE EFFECTIVE CLINICAL TRIALS WILL BENEFIT ALL RESEARCH
• GLOBAL BEST PRACTICES AND LESSONS LEARNED
• CALL TO ACTION
• FUNDING ALWAYS COMES WITH AN AGENDA
• OVERCOMING THE FUNDING VALLEY OF DEATH
• COORDINATED AND FOCUSED FUNDING IS NECESSARY TO ADDRESS AMERICA'S HEALTH CHALLENGES
• NOT EVERYONE IS RECEIVING THE BENEFITS OF THE U.S. BIOMEDICAL RESEARCH ENTERPRISE
• A DIVERSE U.S. BIOMEDICAL RESEARCH ENTERPRISE IS NECESSARY TO PROMOTE HEALTH EQUITY
• HEALTH EQUITY MUST BE EMBEDDED INTO THE U.S. RESEARCH ENTERPRISE
• A SECOND VALLEY OF DEATH: CLOSING THE LAST MILE
• COMPLEX HEALTH CHALLENGES AND PERSISTENT CHRONIC DISEASES
• COORDINATED FUNDING WILL LEAD TO COORDINATED SOLUTIONS
• THE PROMISE OF PUBLIC–PRIVATE PARTNERSHIPS
• THE CURRENT STATE OF THE U.S. BIOMEDICAL RESEARCH ENTERPRISE WORKFORCE
• CONTRIBUTIONS OF INTERNATIONAL SCIENTISTS
• COMPETITIVE FUNDING, EMPLOYMENT, AND SALARIES ARE NECESSARY TO ENSURE FUTURE GROWTH
• DIVERSIFYING THE BIOMEDICAL RESEARCH WORKFORCE
• THE IMPORTANCE OF PHYSICIAN-SCIENTISTS
• REINFORCING THE PIPELINE ACROSS THE EDUCATION CONTINUUM
• 7. A RENEWED AND REVITALIZED U.S. BIOMEDICAL RESEARCH ENTERPRISE IS POSSIBLE

Suggested citation:

National Academy of Medicine. 2024. The State of the U.S. Biomedical and Health Research Enterprise: Strategies for Achieving a Healthier America. M. H. Laitner, A. M. Huang, and S. Takala-Harrison, editors. NAM Special Publication. Washington, DC: The National Academies Press. https://doi.org/10.17226/27588 .

Digital Object Identifier: https://doi.org/10.17226/27588

Printed in the United States of America.

Created: October 1, 2024; Last Update: November 27, 2024.

• Cite this Page National Academy of Medicine; The Learning Health System Series; Takala-Harrison S, Huang AM, Laitner MH, editors. The State of the U.S. Biomedical and Health Research Enterprise: Strategies for Achieving a Healthier America. Washington (DC): National Academies Press (US); 2024 Nov 27. doi: 10.17226/27588
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Randomised controlled trials—the gold standard for effectiveness research

Eduardo hariton , md, mba, joseph j locascio , phd.

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Corresponding Author: Eduardo Hariton, MD, MBA, Brigham and Women’s Hospital, 75 Francis Street, Boston, MA, 02116, USA, [email protected] , Phone: 786-488-4178

Issue date 2018 Dec.

Randomized controlled trials (RCT) are prospective studies that measure the effectiveness of a new intervention or treatment. Although no study is likely on its own to prove causality, randomization reduces bias and provides a rigorous tool to examine cause-effect relationships between an intervention and outcome. This is because the act of randomization balances participant characteristics (both observed and unobserved) between the groups allowing attribution of any differences in outcome to the study intervention. This is not possible with any other study design.

In designing an RCT, researchers must carefully select the population, the interventions to be compared and the outcomes of interest. Once these are defined, the number of participants needed to reliably determine if such a relationship exists is calculated (power calculation). Participants are then recruited and randomly assigned to either the intervention or the comparator group. 1 It is important to ensure that at the time of recruitment there is no knowledge of which group the participant will be allocated to; this is known as concealment. This is often ensured by using automated randomization systems (e.g. computer generated). RCTs are often blinded so that participants and doctors, nurses or researchers do not know what treatment each participant is receiving, further minimizing bias.

RCTs can be analyzed by intentionto-treat analysis (ITT; subjects analyzed in the groups to which they were randomized), per protocol (only participants who completed the treatment originally allocated are analyzed), or other variations, with ITT often regarded least biased. All RCTs should have pre-specified primary outcomes, should be registered with a clinical trials database and should have appropriate ethical approvals.

RCTs can have their drawbacks, including their high cost in terms of time and money, problems with generalisabilty (participants that volunteer to participate might not be representative of the population being studied) and loss to follow up.

USEFUL RESOURCES.

CONSORT Statement: CONsolidated Standards of Reporting Trials guidelines designed to improve the reporting of parallel-group randomized controlled trials - http://www.consort-statement.org/consort-2010

Link to A Randomized, Controlled Trial of Magnesium Sulfate for the Prevention of Cerebral Palsyin the New England Journal of Medicine – A well designed RCT that had a significant impact in practice patterns. http://www.nejm.org/doi/full/10.1056/NEJMoa0801187#t=abstract

LEARNING POINTS.

While expensive and time consuming, RCTs are the gold-standard for studying causal relationships as randomization eliminates much of the bias inherent with other study designs.

To provide true assessment of causality RCTs need to be conducted appropriately (i.e. having concealment of allocation, ITT analysis and blinding when appropriate)

Disclosures: The authors have no financial interests to disclose

• 1. Sibbald Bonnie, Roland Martin. Understanding controlled trials: Why are randomised controlled trials important? BMJ. 1998;316:201. doi: 10.1136/bmj.316.7126.201. [ DOI ] [ PMC free article ] [ PubMed ] [ Google Scholar ]
• 2. Bellad M, Tara D, Ganachari M, Mallapur M, Goudar S, Kodkany B, Sloan N, Derman R. Prevention of postpartum haemorrhage with sublingual misoprostol or oxytocin: a double-blind randomised controlled trial. BJOG. 2012;119:975–986. doi: 10.1111/j.1471-0528.2012.03341.x. [ DOI ] [ PubMed ] [ Google Scholar ]
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