Understanding administrative coding of emergency department visits for unspecified acute allergic reactions

Emergency department (ED) visits for food-related acute allergic reactions enable estimation of temporal trends in food allergy prevalence. To use this approach in New Zealand requires an understanding of the proportion of ED visits coded as 'anaphylaxis, unspecified' or 'allergy, unspecified' that are food-related allergic reactions.

We reviewed all ED presentations of children, coded as 'anaphylaxis, unspecified' or 'allergy, unspecified', from 1988-2011 to the Auckland City Hospital ED. Charts were reviewed independently by two investigators to determine agreement on categorisation of presentations as being food-related acute allergic reactions. We compared ED presentation rates in different time intervals using rate ratios (RR) and 95% confidence intervals (CI).

Sixty-five (29%) of the 221 ED presentations given a discharge code of 'anaphylaxis, unspecified' or 'allergy, unspecified', were a food-related allergic reaction. Inter-observer agreement was very good (kappa >0.80). The ED presentation rate with food-related allergic reactions in 2004-2011 was 98% higher than in 1988-1995 (RR=1.98, 95%CI 1.10-3.72). By contrast, ED presentation rates for non-food-related allergic reactions did not change over these years.

ED presentations for food-related allergic reactions are identifiable from within ED presentations coded as 'anaphylaxis, unspecified' or 'allergy, unspecified'. ED presentations for food-related allergic reactions have increased over time in Auckland.