4.2 | In vivo vs in vitro diagnostic
As previously shown(10), diagnostics with commercially available seafood extracts did not always lead to the correct identification of sensitized patients. None of the tests used, either in vivo or in vitro , was able to detect all selected patients as positive. Indeed, 60,9% per cent of the patients scored positive on SPT for shrimp; 78.3% scored on skin testing with fresh food, 65,8% with cooked food, and 72,4% were positive on the detection of specific IgE to shrimp by ImmunoCAP. Thirty-nine (16.6%) individuals were negative for skin tests with both commercial extracts and raw or cooked shrimp but scored positive on specific IgE assays.
As shown in Table 1, a concordance of commercial SPT and IgE assay for crustaceans was found only in 56% of patients; the concordance rose to 62% between skin tests with raw or cooked fresh shrimp and the in vitro test. Comparing the in-vivo and in-vitro evaluations with cephalopods (squid or octopus) or mollusks (mussels or clams), and even higher heterogeneity of results was observed (Table 1).
No correlation was found comparing IgE levels to seafood extracts, shrimp, cephalopods and mollusks, except for a moderate relationship between cephalopods and mussels (rho 0.634, p <0.001)
To evaluate the prevalence of IgE reactivity to cephalopods or mollusks in shrimp reactive subjects, our patients were extensively studiedin vitro with both extracts and allergenic molecules, using singleplex and multiplex methods. As shown in Table2, IgE sensitization to shrimp was significantly associated with hypersensitivity to cephalopods (p <0.005), but not to mollusks on singleplex testing. Notably, specific IgE levels did not differ in the two patient groups.
On the other hand, when shrimp immunoreactive patients were evaluated by the multiplex system, they were also more frequently positive for crab, lobster, northern and white shrimp, squid, mussel, and clam, but not for oyster, and scallop (Table 2). Crustacean reactivity was accompanied by significantly higher levels of specific IgE towards all extracts tested, except for crab, oyster and scallop, where specific IgE levels did not differ.
From the molecular point of view, IgE reactivity to crustaceans was associated with a significantly higher frequency and higher levels of specific IgE to tropomyosins (both Pen m 1 and Der p 10) and sarcoplasmic calcium-binding protein (Pen m 4), in comparison with the patient that scored negative for specific IgE to crustaceans (Table 2).