Tests To Confirm Drug Allergy in Patients with a History of Possible Immediate Allergic Reactions to Drugs

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The summary below is from the full report titled "Drug Provocation Tests in Patients with a History Suggesting an Immediate Drug Hypersensitivity Reaction." It is in the 15 June issue of Annals of Internal Medicine (volume 140, pages 1001-1006). The authors are D. Messaad, H. Sahla, S. Benahmed, P. Godard, J. Bousquet, and P. Demoly.

What is the problem and what is known about it so far?

Allergic reactions to drugs are common. Some allergic reactions occur after a person has been receiving a drug for some time, while other reactions occur shortly after a person takes the drug and are known as "immediate drug hypersensitivity." Immediate drug hypersensitivity reactions can vary from mild skin rashes to life-threatening reactions associated with difficulty breathing, shock, and even death. Sometimes it is difficult to confirm whether a person has had a true immediate hypersensitivity reaction to a specific drug or type of drug. This lack of certainty can be problematic when the patient needs the specific drug or a related drug again and there is no easy substitute. With some drugs, such as penicillin, doctors can test for allergic reactions by administering small amounts of the drug under the patient's skin in a procedure called skin testing. However, skin testing is not an option for other types of drugs. In some cases, the only way to know whether the patient is really allergic to the drug is to give the drug again and see what happens. This is called a drug provocation test.

Why did the researchers do this particular study?

To report how drug provocation tests were used to confirm drug allergy.

Who was studied?

898 patients with possible drug allergy referred to a hospital in France between September 1996 and August 2001. The researchers did not test patients with severe skin reactions or patients with positive results on skin tests for penicillin or related antibiotics.

How was the study done?

The researchers administered increasing doses of the suspected drug up to the usual daily dose while the patient was carefully supervised in the hospital. The drugs tested included various antibiotics, aspirin, and other anti-inflammatory drugs. The researchers reported the results of the drug provocations tests and recorded how they stopped allergic reactions that developed during testing.

What did the researchers find?

Of the 1372 drug provocation tests that the researchers performed in 898 patients, only 241 (17.6%) results were positive for immediate hypersensitivity allergic reactions. The researchers treated all reactions that developed. No patient died or sustained lasting bad effects from testing.

What were the limitations of the study?

Experienced health care professionals conducted this study in a carefully controlled setting. Drug provocation tests might not be as safe in less experienced hands.

What are the implications of the study?

Drug provocation tests carried out under careful conditions can be a safe and useful way to confirm true drug allergies.