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).