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Routine hospital data analysis suggests the incidence of anaphylaxis is rapidly increasing in England.1 2Although an acute life threatening disorder, anaphylaxis is often managed sub-optimally,3 one of the major difficulties being prompt recognition of the disorder.4 An appreciation of how aetiology varies with age may aid clinicians in arriving at a quick and accurate diagnosis.
Using the Hospital Episode Statistics database, we studied 2323 emergency NHS admissions over the four year period from 1 April 1991 to 31 March 1995, with a primary diagnosis of anaphylaxis (International Classification of Diseases(ICD) 9: 995.0; 999.4). Three cases were excluded because of invalid age codes; 17% of admissions occurred in children aged under 16 (n = 385). Overall, aetiology was recorded for 52% (n = 1207) of admissions, the most commonly recorded triggers being drugs (61%), food (16%), and venom (11%).
Studying age specific aetiology (table 1) reveals that food related anaphylaxis becomes relatively less frequent with increasing age (p < 0.001) whereas the proportion of drug triggered admissions increases with age (p < 0.001). No venom related admissions were noted in infants, but in all other age groups the proportion of venom triggered admissions remained stable.
Differences in age specific patterns of admission may result from variations in susceptibility, exposure, or both. Alternatively, these patterns may reflect recording biases, which may operate differentially. Care also needs to be taken in interpreting these data because aetiology was not recorded for almost half of the anaphylaxis admissions studied. Despite these reservations, in view of the unprecedented number of cases available for study, our findings are likely to provide the most reliable picture of variations in anaphylaxis aetiology with age. Further progress will be dependent on achieving more comprehensive recording of trigger agents, particularly in children, and the development of a more extensive set of ICD codes for anaphylaxis that allows recording of triggers such as nuts and latex.1
Aziz Sheikh is supported by a NHS R&D National Primary Care Award