Exposure Testing (Challenge or Intolerance Testing)
An exposure test is the controlled administration of a medication or food to diagnose allergic reactions.
What is it used for?
Controlled exposure testing with foods or drugs is used for confirming or ruling out allergic reactions, when a conclusive diagnosis could not be reached with the other tests.
How is it done?
The first thing that has to be done when carrying out a controlled exposure test is inform the patient about the test, its usefulness and associated risks. Patients should be provided with an information sheet and asked to sign an informed-consent form.
The tests are carried out in the nursing office, located on the second floor of the Old School of Nursing (Antiga Escola d'Infermeria), where a nurse will carry out the skin tests and some food and medication challenges, or at the Allergology Day Hospital, which has all of the tools for diagnosing and treating any adverse reaction, as well as a doctor and nursing staff who are trained to carry out this procedure.
With drug trials, allergen will be administered through the safest route (orally or intravenously). When necessary, the dose will be divided or the speed of administration reduced, according to the documented adverse reaction and the type of drug being studied.
Once the drug has been administered, patients should remain under observation for several hours so that any delayed reactions can be diagnosed.
Risks
Since the procedure is not without risks, the risk-benefit ratio needs to be assessed before an exposure test can be carried out. As for studies with medications, such testing will only be done with important drugs, meaning, in cases where one medication is more effective than other alternatives (if there are any).
Most reactions triggered by the test are mild, and then diagnosed and treated early. However, severe reactions can occur, such as anaphylaxis and anaphylactic shock.
Alternatives
There are no alternatives to exposure tests, since they represent the last stage of a diagnostic process. However, if a diagnosis can be obtained from the previous tests (skin or blood testing), it may not be necessary to carry these out.