Pediatric anaphylaxis in the emergency department: Performances of dynamic tryptase measurement.

Background: Dynamic measurement of serum acute (sAT) and baseline (sBT) tryptase confirms mast cell degranulation during systemic hypersensitivity reactions, provided timing and interpretation are appropriate. The current consensus formula requires sAT greater than a personalized cutoff value [sAT > (1.2 × sBT) + 2]. Only a few studies have investigated its diagnostic performance in children. Objective: We assessed the diagnostic accuracy of the consensus formula and alternative algorithms for interpreting tryptase levels in pediatric patients with suspected anaphylaxis. Methods: Medical records of suspected anaphylaxis referred to the pediatric emergency department of the University Hospitals of Marseille (France) from 2011 to 2020 were retrospectively reviewed. Clinical and laboratory data, including total tryptase and allergy evaluations, were collected. Anaphylaxis was defined as a sudden-onset, perceived life-threatening systemic reaction at the time of physician assessment. Inclusion criteria were suspected anaphylaxis and at least one tryptase determination. The diagnostic performance of the consensus formula was compared to 5 alternative tryptase interpretation algorithms. Results: Among 315 patients (median age, 7.8 years; 317 emergency department visits), 175 (55%) were categorized as cases. Food-induced anaphylaxis was diagnosed in 82%, and 92 (52.6%) had two or more tryptase determinations. The highest diagnostic performance was achieved by the sAT/sBT ratio. A cutoff for sAT/sBT ratio of >1.74 yielded 66.7% sensitivity, 90.0% specificity, 96.8% positive predictive value, and 24.3% negative predictive value. The retrospective study design was a major limitation. Conclusion: Compared to the current consensus formula, a sAT/sBT ratio above 1.74 may enhance the diagnostic performance of dynamic tryptase measurement in children with suspected anaphylaxis.