Statistical analysis
Categorical variables are expressed as number (percentage), and continuous variables are expressed as either mean (standard deviation) or median (range) when appropriate. Univariate and multivariate analyses were used to identify independent associations between demographics and clinical characteristics with AAI prescription. The chi-squared statistic and independent samples t-test were used to compare categorical and continuous variables between groups in univariate analysis, respectively. Variables with a P value of 0.1 or less from univariate analysis were included in multivariate logistic regression to determine which variables were independently associated. AP value of less than 0.05 was considered statistically significant for the multivariate analysis. SPSS Statistics version 20 (IBM, Armonk, NY, USA) was used for all analyses. The incidence rates were calculated by the number of patients divided by the number of total estimated population of Hong Kong between 2009 and 2019. The AAI prescription rates were calculated by dividing the number of AAI prescriptions by the number of patients with anaphylaxis. Population statistics from the Census & Statistics Department (Hong Kong Government) were extracted for calculations11. Our Census used 19 years old as the cut-off age for pediatric population, thus estimates for the breakdown of pediatric and adult anaphylaxis incidence rates were calculated using population data for <20 and ≥20 years, respectively. This study was reviewed and approved by the Institutional Review Board of the Joint Chinese University of Hong Kong – NTEC Clinical Research Ethics Committee.