Trial Types


Types of clinical trials

Interventional Clinical Trials

The interventional clinical trial is any research study that prospectively assigns human participants to one or more health-related (preventive, diagnostic or therapeutic) interventions with the aim to evaluate effects on health outcomes. Interventions include, but are not limited to medications, behavioral interventions, imaging procedures, radiation, biological, genetic etc.

Expanded Access Clinical Trials

Expanded Access trials are those who use investigational new drug outside of a clinical trial as defined by the protocol. In certain serious or life-threatening conditions patients are treated with drug although they do not fulfill criteria defined by clinical trial protocol (e.g. inclusion or exclusion criteria are not satisfied).

Observational Study

In an observational study, investigators observe subjects and measure variables of interest without assigning treatments to the subjects. Received treatment (diagnostic method, preventive measure etc.) is usually administered as part of standard care. More information can be found in the book ublished by "Agency for Healthcare Research and Quality (US)". Book is available through the link:

Developing a Protocol for Observational Comparative Effectiveness Research: A User's Guide

Observational Study Based on Patient Registry

Registry trials are a subgroup of observational studies where information about the patient (or participant) is collected within the registry. Those studies are particularly suitable, but not limited to, for evaluation of the natural history of the disease, long follow-up for delayed or long-term toxicity or benefits of interventions, trials where blinding is unethical etc. Further information on registry trials may be found in excellent book published by "Agency for Healthcare Research and Quality (US)". Book is available through following link:

Registries for Evaluating Patient Outcomes, 3rd edition