Mollusk allergy in shrimp-allergic patients: still a complex diagnosis.
An Italian multicenter study
Abstract
Introduction |Shellfish allergy is an important cause
of food allergies worldwide. Both in vivo and in vitro
diagnostics failure nowadays is caused by the poor quality of the
extracts associated with the scarce availability of allergenic molecules
in the market. It is known that not all patients with shellfish
allergies experience adverse reactions to mollusks. It is still unclear
how to detect and diagnose correctly these patients. Aim
|To investigate the features of shrimp-allergic patients
either reactive or tolerant to mollusks, with the currently available
diagnostic methods. Methods| Nineteen centers,
scattered throughout Italy, participated in the study, enrolling
patients allergic to shrimp with or without associated reactions to
mollusks. Patients underwent skin tests using commercial extracts or
fresh raw and cooked foods, and IgE reactivity to currently available
allergenic extracts and molecules was measured in vitro.
Results| Two hundred and forty-seven individuals with
a history of adverse reaction to crustaceans participated in the study.
Only 47.8% of them reacted after cephalopod or bivalve ingestion. None
of the tests used, either in vivo or in vitro, was able to
detect all selected patients. Accordingly, a great heterogeneity of
results was observed with an agreement between in vivo and
in vitro tests ranging between 52% and 62% of cases. Skin tests
were able to identify the cephalopod and bivalve reactors (p
<0.001), also using fresh cooked or raw food (p
<0.001). The reactivity profile of mollusk reactors was
dominated by Pen m 1, over Pen m 2 and Pen m 4 compared to the tolerant
subjects, but 33% of patients allergic to shellfish were not detected
by any of the available molecules. A higher frequency of shrimp
hypersensitivity was recorded in northern Italy, while mollusk
reactivity was more frequent in the center-south. Conclusion
|The current diagnostic methods are inadequate to predict the
cross-reactivity between crustaceans and mollusks. The detection of
mollusks hypersensitivity must still rely on skin tests with fresh
material. There is no need to exclude mollusks from shrimp allergic
patients’ diet unless clinical history, the available diagnostic
instruments, and/or tolerance tests support such a decision. Primary
sensitization to mollusks seems possible.