The 411 on allergies and patient safety
Dr Bryan Fernandes, consultant allergist, gives us the low down on allergies and why getting allergy documentation right can help us keep patients safe.
When we think about allergies we often associate things like nuts, gluten and dairy. In the hospital setting the associations are much wider and understanding allergens can be the difference between life and death.
What are allergens?
Allergens are foreign and apparently harmless molecules that induce an abnormal immune response, which causes an allergic reaction.
Almost any drug can cause an allergic reaction but the common ones are antibiotics (particularly penicillin), non-steroidal anti-inflammatory agents (i.e. Ibuprofen), opiates, general anaesthetic drugs, iodinated contrast media (used in CT scans), anti-epileptic drugs, and chemotherapy drugs.
How is a drug allergy different from an intolerance or side-effect?
A drug allergy is an abnormal reaction of the immune system to a medication. It is commonly classified based on onset of reaction:
• Immediate: if it occurs within an hour after drug intake
• Delayed: if it is more than an hour after drug intake
Immediate-onset drug allergy typically presents with hives, swelling, or a severe life threatening allergic reaction called anaphylaxis. Delayed-onset drug allergy usually presents as rashes but some reactions can be severe.
A drug intolerance is a term used by some to describe drug side effects, which are not immune mediated reactions but an undesirable pharmacological effect that may occur at low or usual doses of the drug. These may be reactions such as antibiotic-induced diarrhoea or NSAID-induced gastritis and non-specific symptoms such as myalgia, fatigue, headache etc.
What is cross-reactivity and why does it matter?
When a person becomes allergic to a drug there is a possibility of cross-reactivity with other similar drugs. This occurs with drugs which have close structural similarity or immunologically similar metabolites. This information is important to know because giving a drug which is cross-reactive to the drug to which the patient is allergic to can also cause an allergic reaction, which can sometimes be severe. For example, antibiotics such as cephalosporins can cross-react with penicillin antibiotics.
Why is accurate allergy documentation so important?
Analysis of patient safety incidents reported to the National Reporting and Learning System (NRLS) over an eight year period showed that there were about 18,000 incidents involving drug allergy, out of which there were six deaths and 19 ‘severe harms’ and 4,980 ‘other harms’. The majority of these incidents were due to a drug that was administered for a patient with a previously known allergy to the same or cross-reactive drug.
When a patient has experienced an allergic reaction to a drug their medical records are frequently not updated or there may be insufficient clinical details of the original reaction. Therefore with passage of time it becomes difficult to assess the severity of the reaction the patient experienced. In some clinical situations, it may be necessary to re-expose the patient, for example when an alternative drug is less effective or the patient has multiple drug allergies. However, with incomplete clinical details of the original reaction it may not be possible to make a judgement on whether a reaction was immunologically mediated, and hence assess the risk of an allergic reaction on re-exposure, which can be fatal.
The National Institute for Health and Care Excellence (NICE) recommends to document drug allergy status as ‘drug allergy, ‘none known’ or ‘unable to ascertain’ and as a minimum to have the following information recorded – drug name, signs, symptoms and severity of the reaction, the date when the reaction occurred. They suggest recording new drug allergic reactions in a structured way.
What information do you need if a patient is being referred to you following an anaphylaxis?
If a patient is referred to our service it is useful to have as much details of the reaction as mentioned above. If the reaction was during a general anaesthetic procedure then we need a specific form to be sent to us by the anaesthetist involved in the procedure.