According to a new ‘yardstick’, there are people for whom diagnosis and treatment of anaphylaxis are difficult because the cause is unknown and therefore labelled ‘idiopathic.’
“Although idiopathic anaphylaxis (IA) is relatively rare, medical professionals do run across it,” says anaphylaxis researcher Melody Carter, MD, lead author of the yardstick. “Since avoidance is the first line of defence in preventing anaphylaxis, anyone who hasn’t had the cause identified is at a disadvantage, including physicians who are treating those with anaphylaxis. We developed the “Idiopathic Anaphylaxis Yardstick” to help physicians who might be searching for guidance on next steps after their patient has an anaphylactic reaction of an unknown origin.”
According to the yardstick, a patient history is a vital step in diagnosing IA. Several diseases and disorders have symptoms which mimic anaphylaxis related to an allergy, and some causes of anaphylaxis have been discovered or are better recognised in recent years. Thus, there are many diagnoses labelled as ‘differential’ – not caused by allergy but a reaction to something else. The patient history must include events that happened just before the event – foods that were eaten, drugs taken, activities (that is, exercise) insect stings or exposure to heat or cold. The time, location and duration of the event should also be considered.
“Advances in diagnostics have led to the discovery of disorders that were likely the cause of IA for many patients in the past,” says allergist Phil Lieberman, MD, ACAAI member and co-author of the yardstick. “The yardstick contains a detailed discussion of the disorders that should be considered including alpha-gal, clonal mast disease, drug/alcohol induced flushing, tumour-related flushing and hereditary alpha tryptasaemia syndrome. We outline diseases and disorders that can cause anaphylaxis or present with symptoms associated with anaphylaxis in order to assist allergists in examining a broad spectrum of possible causes. We also discuss laboratory tests that are essential diagnostic tools.”
The yardstick has special sections that address paediatric patients and also provides suggestions for how to proceed with patients who do not respond to other treatments.