Objectives & Background Anaphylaxis is under-reported in emergency settings and the potential for diagnostic confusion with acute asthma has been reported, especially in children who experience predominantly respiratory symptoms. However, no previous study has directly investigated the probability of unrecognised anaphylaxis in either adults or children presenting with acute asthma.

Methods A retrospective case note analysis of children admitted with acute asthma to Bristol's Paediatric Intensive Care Unit (PICU) was conducted. Cases were identified from the PICU admission database and children with other pre-existing respiratory disease were excluded. A total of 73 cases remained eligible for inclusion and were subjected to analysis using the Brighton Collaboration Case Definition (BCCD) for anaphylaxis. Cases with evidence of anaphylaxis were assigned a level of diagnostic probability from 1 (high) to 3 (low) based upon the BCCD.

Results The case notes of 84 children admitted to Bristol Royal Hospital for Children's PICU were obtained. 11 cases met exclusion criteria leaving 73 eligible for inclusion in the study. Clinical features consistent with a diagnosis of anaphylaxis were discovered in a total of 13 cases (17.8%). A single case (1.4%) met the criteria for level 1 (high probability) and the remaining 12 cases (16.4%) met criteria for level 2 (intermediate) probability. Following careful clinical review of each case meeting the BCCD, it became clear that anaphylaxis was probable in 3 cases (4.1%). The clinical features exhibited in the other 10 cases could each be more reasonably explained by the original diagnosis of acute asthma and/or concurrent infection.

Conclusion The results support the conclusion that some cases of anaphylaxis are unidentified and managed as acute asthma in children. The local frequency was estimated at 4.1% of children admitted to PICU but larger prospective multi-centre studies are required to better define the true prevalence nationally.