Defining baseline variability of serum tryptase levels improves accuracy in identifying anaphylaxis

Acute increases of ≥20% + 2 ng/mL (20 + 2 rule) over basal serum tryptase (BST) is the recommended threshold supporting a clinical diagnosis of anaphylaxis. Prospective studies have demonstrated high sensitivity for this algorithm after parenteral exposure, but specificity has not been evaluated.We sought to define a serum tryptase change that distinguishes baseline variability from anaphylaxis on the basis of intraindividual variation in...