4.3 | Sensitization profiles and clinical correlations
One hundred-eighteen (47,8%) patients enrolled because allergic to crustaceans, reported also moderate (80.5%) to severe (19.5%) reactions after ingestion of mollusks.
There was no difference in the frequency of reactive episodes related to sex or age.
Interestingly, a higher risk of developing a severe reaction after mollusks intake was associated with skin test reactivity to commercial extracts of cephalopod (OR: 4.81; CI 1.8-9.3; p <0.001) or bivalve (OR: 14.970; CI 4.2-53.3; p <0.001). Similarly, mollusk reactors showed a high frequency of reactivity to both raw (OR: 4.492; CI 1.9-10.4; p <0.001) and cooked squid (OR: 3.040; CI 1.3-7.3; p <0.001), and to both raw (OR: 20.907; CI 5.8-75.2; p <0.001) and cooked clam (OR: 17.249; CI 3.1-41.1; p <0.001).
The multiple logistic regression analysis, when simultaneously adjusted for the presence of specific IgE to all the extracts studied, age, and sex, showed a significant relationship between a history of adverse reaction to mollusks and IgE reactivity to both cephalopods (ORadj 4.0, 95% CI 1.5-10.7, p <0,01) or bivalve (ORadj 7.6, 95% CI 3.1-18.6, p <0.0001) extracts. Moreover, as shown in Table 3, allergy to mollusks was associated with IgE reactivity to northern shrimp (Litopaenaeus setiferus ), squid (Loligo spp.), mussel (Mytilus edulis ), oyster (Ostrea edulis ), clam (Ruditapes spp.), and scallop (Pecten spp.) extracts. Pen m 1 (Penaeus monodon tropomyosin) hypersensitivity was significantly associated with an increased risk of severe reaction to mollusks.
Three patients scoring SPT positive to crustaceans showed in vitro sensitization to bivalves (both oyster and mussel) in two cases and squid in one case, with no sign of IgE reactivity against any the extracts and molecules of crustaceans in vitro , with only a low reactivity in one case to paramyosin (0.24 kU/L) and tropomyosin (0.39 kU/L) from house dust mite (Der p 11 and Der p 10 respectively).
As summarized in Figure 1, the molecular sensitization profile was dominated by Pen m 1, but more frequently in those who did not tolerate mollusks. Moreover, mollusks reactors had also two times higher frequency of sensitization to arginine kinase and sarcoplasmic Ca++ binding protein (Figure 1). Interestingly, the number of crustacean allergic patients who did not react to any of the molecules currently available for in vitro diagnostics was very high, particularly among those who tolerated cephalopods and bivalves (43%).
4.4 |Geographical differences in seafood sensitization profiles
When we analyzed the data as a function of the geographical distribution of patients, we found a significantly higher frequency of sensitization to crustaceans in northern Italy, irrespective of the diagnostic tests used (skin prick test, prick-prick test with fresh or cooked food, and specific IgE measurement for allergen extracts), whilst in centre-southern Italy, a more frequent sensitization to Bivalvia was recorded (Figure 2 A-C). This observation was in keeping with a higher frequency of reactions to bivalve in the south, whilst the sensitization levels to cephalopod were comparable among south and north (Figure 2 D).