State of Clinical Trials

>> Project Summary


State of Clinical TrialsImproving the Public Interface for Use of Aggregate Data in

Project Status: Current is a registry of human clinical research studies hosted by the U.S. National Institutes of Health, through its National Library of Medicine (NLM), in collaboration with the Food and Drug Administration (FDA). Studies listed in the database are conducted in all 50 U.S. states and in 174 countries. The purpose of is to provide a central resource for those seeking information on individual clinical research projects and to increase visibility of human subjects' research.

Federal law requires the registration of all trials of drugs and biologics, including controlled, clinical investigations other than phase I investigations of a product subject to FDA regulation, and trials of devices, including controlled trials with health outcomes of a product subject to FDA regulation (other than small feasibility studies) and pediatric postmarket surveillance studies. "Applicable clinical trials" generally include interventional studies (with one or more arms) of drugs, biological products, or devices that are subject to FDA regulation, meaning that the trial has one or more sites in the U.S., involves a drug, biologic, or device that is manufactured in the U.S. (or its territories), or is conducted under an investigational new drug application (IND) or investigational device exemption (IDE).


What is the issue?

Many doctors and patients think that clinical trials have become too cumbersome and expensive, and may not even be answering the most useful questions. The first step in improving this situation is to evaluate the current state of clinical trials. The registry provides information regarding characteristics of past, current, and planned clinical studies to patients, clinicians, and researchers; in addition, registry data are available for bulk download. It's very useful for patients who want to participate in clinical trials because it's searchable by keywords relating to conditions, interventions, study sites, and other parameters. But until now, there hasn't been a good way for researchers to access and analyze this treasure trove of data to learn more about the characteristics—and effectiveness—of clinical trials as a whole. Issues related to data structure, nomenclature, and changes in data collection over time present challenges to the aggregate analysis and interpretation of these data in general and to the analysis of trials according to clinical specialty in particular. Improving usability of these data could enhance the utility of as a research resource.


More information about

When was established by the National Library of Medicine in 2000, registration of trials was voluntary. In 2007, federal legislation was passed that required that most clinical trials in the United States be registered on Registration for observational studies is voluntary. The registry requires a summary of each trial and some basic information, such as number of people enrolled, location of the study, type of study, sponsor, and investigator. Initially there was no provision for posting results and adverse effects, but now both are required for certain trials. Currently, there are more than 100,000 trials on the site, and more than 300 are added every day.

This project aimed to create a restructured version of the database that analysts could more easily use to study various aspects of clinical trials in the United States, including:

  • Understanding the current state of clinical trials as a whole
  • Comparing trials within or between different medical specialties, such as oncology, pediatrics, or cardiology
  • Looking for unmet need in a particular specialty
  • Seeing what’s already been done in a specialty before designing another trial in that specialty


What did we do?

No. 1Created AACT (Aggregate Analysis of database
We arranged information from into a database that allows researchers and analysts to perform analyses on a study dataset (a group of several studies) and not just within an individual study. AACT is available for download on the CTTI website.


No. 2Developed a method of categorizing trials by clinical specialty
We created a method to identify and group the clinical trials by specialty, such as pediatrics, infectious diseases, etc. This makes it easier for researchers to understand what trials have been done in each medical specialty, or to compare trials between specialties—for example, to compare the average number of participants in cardiovascular trials to those in oncology trials.


No. 3We began analyzing the clinical trials enterprise using AACT
Our group has already begun using AACT to do research into how clinical trials are conducted in the specialties of cardiology, mental health, and oncology. This research has raised questions about differences in trial size and study design among the specialties.


What did we produce?

We produced AACT: a searchable, downloadable, accessible database that analysts can use to do research about clinical trials registered on

In addition to the AACT database itself, we created a detailed data dictionary providing documentation about the source, coding, and history of variables collected in AACT; a high level data dictionary containing a summary of these variables; and guidelines to consider when planning a statistical analysis of the database. These tools help analysts to better interpret their results from AACT. Several papers have been published and presentations given about creating AACT and research performed using AACT, including papers focused on different medical specialties.


What are the next steps?

  • Continue to publish on the state of clinical trials based on research done using AACT. CLICK HERE for an updated list of presentations and publications.
  • Update AACT periodically. CLICK HERE for the latest version of AACT.


Snapshot of CTTI's State of Clinical Trials Project

Snapshot of CTTI's State of Clinical Trials Project


Contact Us

The project manager for this project is Sara Calvert. Please send your questions, comments, or feedback regarding AACT or the State of Clinical Trials Project to



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CTTI encourages the use of all materials listed on this site in the pursuit of improving the clinical trials enterprise. Our recommendations, tools, meeting summaries, and more are available to the public for free. We do ask that you acknowledge the source whenever using or referencing CTTI materials. Read our Citation Policy here.