DIAGNOSIS OF “PENICILLIN ALLERGIC” OFTEN INCORRECT

Of those who think they are allergic to penicillin, how many actually are? Being labeled penicillin-allergic is extremely common, but typically claims are unsubstantiated. Current estimates claim 20% of the global population believes they are penicillin allergic.

Yet evidence indicates 90%–99% of those individuals with a reported penicillin allergy are not truly allergic. Most diagnoses are made in childhood due to unrelated events. A child is prescribed a penicillin-type drug, then has some mild medical event, a rash, or other completely unrelated condition. Someone will say “they must be allergic to penicillin!” and the label of PCN-allergic applied. No testing is typically done.

There is the potential for harm when this occurs. Giving a different antibiotic often results in dangerous consequences.  Most surgery patients receive second-line antibiotic prophylactically, causing a 50% increase in the risk of developing a surgical site infection.  

And there are other risks, including an increase in healthcare-associated infections,  increased odds of a secondary C. diff infection, as well as an increased risk of getting a MRSA or some other drug-resistant infection (VRE).

Maybe most importantly, the label of penicillin allergy directly impacts the responsible and appropriate use of antibiotics. associated with the development of resistant bacteria.

Only a minority of surgical patients have the opportunity to undergo testing before surgery. Testing protocols are rarely utilized.

Penicillin belongs to an important class of drugs and are generally very effective for many common bacterial infections. Numerous examples of this class of drug are prescribed including derivatives such as ampicillin and amoxicillin, as well as cephalosporins, monobactams, and carbapenems. Although they are considered relatively benign medications, antibiotics can have dangerous consequences.

A true drug allergy accounts for very few of all the reported adverse drug reactions. The determining factor is the type of allergy. A rash is a common result of one type, but produces little response by the body. The real danger is when an anaphylactic reaction occurs.

Hypersensitivity reactions are a serious problem in the use of these drugs, although the frequency is quite low (1 and 5 per 10 000 cases of penicillin therapy). The most dangerous adverse event is anaphylaxis, with complications including nausea, vomiting, itching, wheezing, swelling of the throat and ultimately, cardiovascular collapse, often a fatal development.

Patients who give a clear history of anaphylaxis or severe cutaneous reactions are easily categorized as being at high risk. But typically, the situation is not so clearly defined. Far too common, is the typical ‘no recollection of the event’.

We need to review how patients are assessed and defined as ‘ALLERGIC’. What are the best testing strategies? These are important questions, both from the perspective of inappropriate antibiotic use, and the rare but potentially-fatal anaphylactic reaction. A testing strategy is needed, providing better answers to these critical questions.