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A natural radioactive gas produced by the decay of uranium found in soil, rock or water. Radon gas is invisible, odourless and tasteless. Radon can move freely through the soil allowing it to enter the atmosphere or seep into buildings.


A clinical trial method in which the subjects are randomly distributed into groups which are either given the test drug or which serve as the control group.


In a clinical study protocol the rationale is the reason why a clinical study is needed, and which questions researchers want to answer.

Reactive arthritis

Reactive arthritis is a type of arthritis, or joint inflammation that occurs as a “reaction” to an infection somewhere else in the body.


The period during which a trial endeavours to identify and enrol patients.


Recruitment status

Indicates the current recruitment stage of a trial, whether the trial is planned, ongoing, or completed. Designations can include:

- Not yet recruiting: patients are not yet being enrolled
- Recruiting: patients are currently being enrolled
- Active, not recruiting: patients are being treated or examined, but enrolment is completed
- Completed: patients are no longer being examined or treated in the context of the trial
- Suspended: recruitment of patients has halted prematurely, but will potentially resume
- Terminated: recruitment of patients has halted prematurely, and will not resume
- Withdrawn: trial halted prior to enrolment of first patient.


The last part of the colon.


Recurrence means cancer that has recurred or come back. This usually happens after a period of time during which the cancer could not be detected. The cancer recur in the same place as the original (primary) tumor or to another place in the body.

Red blood cell

A type of blood cell that is made in the bone marrow and is found in the blood. Red blood cells contain hemoglobin, which carries oxygen from the lungs to all parts of the body. Evaluation of the number of red blood cells in the blood is usually part of a complete blood cell (CBC) test.


In medicine, describes a disease or condition that does not respond to treatment.


The return of a disease or the signs and symptoms of a disease after a period of improvement.


A period free of active disease with few or no symptoms.

Remission stage

Reduction in or disappearance of signs and symptoms of cancer. In partial remission, only some of the signs and symptoms of cancer have disappeared. In complete remission, all signs and symptoms of cancer have disappeared, even though cancer may still be in the body.

Research study

Carefully planned studies that observe or treat patients in order to develop or discover new treatments or medications. Researchers want to see how well a drug works, how it can be used safely, and learn how to prevent, screen for, better diagnose and treat health issues.


Respiratory therapist

A specialist who helps patients improve their breathing capacity.

Retinal detachment

A retinal detachment means the retina has been lifted or pulled from its normal position. It can occur at any age, but is more likely in people over age 40.


Any of various synthetic or naturally occurring analogs of vitamin A.

Rheumatoid arthritis

A form of arthritis that causes pain, swelling, stiffness and loss of function in your joints. It can affect any joint but is common in the wrist and fingers.

Rheumatoid factor (RF)

An autoantibody of high molecular weight that reacts against lgG immunoglobulins and is often present in rheumatoid arthritis.


A steroid that prevents the release of substances in the body that cause inflammation. Rimexolone is used to treat eye inflammation caused by infections, injury, surgery, or other conditions.