Methods: Nineteen patients with history of adverse reactions upon shrimp ingestion and positive sIgE and/or SPT underwent OFC. Shrimp SPT, serum sIgE and rPen a1 were analyzed. Exclusion criterion included patients on dust mite immunotherapy (DIT). Fisher’s exact test, Kruskall-Wallis and receiver operating characteristic analysis were performed.
Results: Nine were shrimp tolerant (ST), while 10 were shrimp allergic (SA; 5 failed OFC and 5 had a history of anaphylaxis). sIgE and rPen a1 were higher in SA than ST (median kU/L:sIgE=10.2 vs 0.8[p=0.004]; rPen a1=3.79 vs 0.09[p=0.006], respectively). rPen a1≥0.72 kU/L identified patients as SA in 84% of this population (AUC=0.86;95%CI:0.68-1.00; sensitivity=80%, specificity=89%). sIgE≥1.12 kU/L identified patients as SA in 84.1% of this population (AUC=0.89;95%CI:0.71-1.00; sensitivity=90%, specificity=78%). No differences were observed in SPT between SA and ST. Three patients on DIT who passed OFC were evaluated separately and had elevated sIgE and rPen a1 compared to the ST group (median kU/L:sIgE=33.1 vs 0.8[p=0.012]; rPen a1=22.5 vs 0.09[p=0.007], respectively).
Conclusions: rPen a1≥0.72kU/L and/or shrimp sIgE≥1.12kU/L are useful to predict clinical reactivity in 84% of patients with suspected shrimp allergy potentially obviating the need for an OFC. Since DIT may modulate IgE levels, caution interpreting shrimp sIgE for IT recipients is recommended.