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Common pitfalls in diagnosing anaphylaxis

PHILADELPHIA — When anaphylaxis is suspected, diagnostic criteria, symptoms, risk factors, clinical history and pitfalls are important to consider in confirming the diagnosis, according to a presentation at the ACP Internal Medicine Meeting.

“The prevalence of anaphylaxis seems to be increasing. One thing that is for sure is that anaphylaxis is underrecognized and undertreated,” Olajumoke Fadugba, MD, assistant professor of clinical medicine in the division of allergy, pulmonary, and critical care at the University of Pennsylvania, said during her presentation.

More than half of patients who present to the ER with anaphylaxis are misdiagnosed, she said, but even when correctly diagnosed, epinephrine, which is the first-line therapy for anaphylaxis, is frequently not administered.

“The reason it is tough to make the diagnosis is because anaphylaxis can present in so many varied ways and sometimes in atypical and unpredictable ways,” Fadugba said.

The National Institute of Allergy and Infectious Disease and the Food Allergy and Anaphylaxis Network jointly proposed three criteria in which one can make a diagnosis of anaphylaxis:

• Acute onset of symptoms within minutes to hours involving the skin, mucosal tissue or both, which may include generalized hives, pruritus or flushing and swollen lips, tongue or uvula plus respiratory compromise and/or reduced BP or associated symptoms of end-organ dysfunction, such as syncope, dizziness and tachycardia;
• Two or more of the following symptoms shortly after a likely allergen exposure: generalized hives, itch-flush, swollen lips, tongue or uvula; respiratory compromise; reduced BP or associated symptoms; or persistent gastrointestinal symptoms; and
• Reduced BP after being exposed to a known allergen.

The most common symptoms of anaphylaxis are cutaneous, followed by respiratory, gastrointestinal and cardiovascular, Fadugba said. There are also risk factors and comorbidities in anaphylaxis that are important to pay attention to, she said, including asthma, CVD and respiratory diseases, such as COPD.

“It is important to remember that 10% to 20% of patients with anaphylaxis do not have cutaneous findings, so you cannot always rely on the rash or hives,” she said.

Fadugba noted several pitfalls in diagnosing anaphylaxis, including:

• the absence of hypotension or shock;
• the absence of urticaria;
• missed symptoms during anesthesia because the patient is asleep or the rash not obvious;
• first manifestation of allergy so there is no clinical history;
• mistaken as asthma exacerbation; and
• no history of severe reaction.

“In making the diagnosis, clinical history of reactions and symptoms is key,” Fadugba said.

Lab tests for mast cell mediators, such as histamine and tryptase, that can be helpful in supporting diagnosis, she added.

“Diagnosis of anaphylaxis requires application of diagnostic criteria as well as clinical judgement, with caution to avoid diagnostic pitfalls,” she said. – by Alaina Tedesco

Reference:

Fadugba O. Allergic reactions: Urgent and emergent hospital management. Presented at: ACP Internal Medicine Annual Meeting. April 11-13, 2019; Philadelphia.

Disclosure: Fadugba reports no relevant financial disclosures.