Statistical analysis
All patients participating in this study belong to one of the following two groups for analysis: the group with antihypertensive treatment (β-blockers or ACEI) and the group without such treatment. The analyses concerning the outcome “systemic adverse event” are based on the patients who completed the up-dosing phase of immunotherapy, while analyses concerning the outcome “systemic sting reaction” are based on all patients included in the study.
The primary outcome and secondary outcomes were analyzed using logistic linear mixed models with a random intercept. This model type takes into account the clustered structure of the data, i.e., observations clustered in the different participating centers. Parameters, having a p-value <0.15 in the univariable model analysis were kept for further analysis with multivariable models. For further parameter reduction, the Bayesian information criterion (BIC) was calculated as a measure of the relative quality of the models. However, age and taking antihypertensive treatment were always kept in the multivariable models for the outcome “systemic adverse event” as well as for the outcome “systemic sting reaction.” For these outcomes, complete case model analyses were performed, if missing data in parameters of interest were rare (<1%). Otherwise, missing at random was assumed, and multiple imputations were conducted with 50 imputations taking into account the cluster design. The level of significance was set at 0.05.
All analyses were performed using the statistical software R (version 3.6.3) with the lme4 package (version 1.1-23) to carry out multilevel modeling and the MICE package for the multiple imputation analysis (version 3.8.0).21,22