Tropomyosin-based cross-reactivity and asymptomatic shellfish sensitization in patients with perennial allergy.

Background: Mite, cockroach, and shellfish (crab, clam, and shrimp) proteins share allergenic epitopes. The determination of specific IgE (sIgE) against cockroach (Blattella germanica, relevant in asthma) and shellfish allergens (relevant in food allergy) using whole-body extracts necessitates detailed knowledge of IgE cross-reactivity.

Objective: This study aimed to evaluate whether cross-reactivity between aeroallergens and food allergens is clinically relevant and whether subjects with mite and/or cockroach sensitization are at risk of false-positive results in shellfish food allergy diagnostics.

Methods: In this cross-sectional, single-center study, we recruited 200 patients with elevated sIgE against ≥1 allergen at random from our outpatient clinic and assessed allergic comorbidity. We analyzed sIgE against mites (Dermatophagoides pteronyssinus, Dermatophagoides farinae, or Blomia tropicalis), German cockroach (B. germanica), crab, clam, and shrimp whole allergen extract, as well as sIgE against mite tropomyosin Der p 10 and shrimp tropomyosin Pen a 1 (in a subpopulation), using automated ImmunoCAP Specific IgE Tests.

Results: During allergologic assessment, two participants reported previous anaphylaxis to fish and/or seafood and were excluded from further analysis. The final study population comprised 150 female and 48 male participants. Of these, 93 presented with positive sIgE against mites. As expected, participants with mite sensitization displayed an elevated prevalence of perennial asthma or allergic rhinitis (p < 0.001). Further, they were more often sensitized to German cockroach, crab, claw, or shrimp (each p < 0.001). Der p 10 and Pen a 1 sIgE levels were below the cutoff level (<0.35 kU/L) in all subjects. However, the correlation analyses revealed that tropomyosin sIgE explained between 24% and 55% of the variance (R²) in sIgE against clam, crab, German cockroach, or shrimp (each p < 0.001).

Conclusion: Patients with mite sensitization have higher asymptomatic sIgE levels to shellfish. Even in patients with anti-tropomyosin sIgE levels below the cutoff level, anti-tropomyosin sIgE correlates strongly with sIgE against German cockroach, crab, clam, and shrimp. Our findings suggest large-scale false-positive results for sIgE to shellfish when analyzing patients with mite- or cockroach sensitization.