Terms starting with O


The objective is the reason for performing a clinical study, which is usually to learn more about disease and treatments and improve medical care. For example the objective of a clinical study might be to test a new treatment for diabetes to see if it is both safe and effective.

Observational Study

An observational study investigates health outcomes amongst groups of people in the course of their everyday lives at home, work, etc. doing what they normally do and receiving whatever medications or treatments that are part of their normal standard care. In these types of studies, investigators do not assign participants to treatment groups or assign specific treatments, they merely observe and record health status and health-status changes.

Observational Study Model

An observational study model is the general design of the strategy for identifying and following up with participants during an observational study. (CTG)

Observational Study Monitoring Board

An observational study monitoring board is the group that monitors safety and data for observational studies.

Observer Assessment

An observer assessment gauges a patient's condition using an observer, such as an investigator, nurse, clinician, family member, etc. The observer relies on his or her judgment to assess the participant. Important to note, an interviewer who simply records a patient's self assessments is not making an observer assessment.

Office for Human Research Protection

The Office for Human Research Protection is the federal government agency within the Department of Health and Human Services that ensures and protects the rights and safety of people who participate in government-funded research.

Open to Enrollment

Open to enrollment means that a clinical study is currently accepting applications from potential participants.

Open-label Trial

An open-label trial is a clinical study in which both participants and investigators know which medicine or treatment each participant is receiving.

Other Adverse Event

Other adverse events are not serious in that they do not result in significant health problems or reduce quality of life.

Other Study IDs

Other study IDs are identifying numbers other than the National Clinical Trial (NCT) number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other clinical study registries and National Institutes of Health grant numbers. (CTG)


Clinical outcomes are results that reflect disease, symptoms, signs or laboratory abnormalities which are the target outcomes in clinical studies.

Outcome Measure

An outcome measure is the method investigators use to determine the effect of an intervention/treatment. In observational studies, this is a measurement or observation that investigators use to describe patterns or traits of diseases, or the association diseases have with various exposures, risk factors, or treatments.

Outcomes Research

Outcomes research studies (in a broad sense) the effect the healthcare system has on the health and well-being of patients and populations.


Outliers are results that fall outside of the range of expected results from a clinical study.