Phadia’s F290 test is used to detect blood levels of the IgE (antibodies) responsible for allergic reactions to oysters. While some individuals may be allergic only to oysters, cross allergies to mussels and other molluscs (clams, scallops, squid, etc.) can be expected. Many people are also allergic to shellfish (shrimp, lobster, crayfish, etc.), and multiple seafood allergies are common. The interpretation chart accompanying the result expresses the probability of an allergic reaction to oysters (and possibly other molluscs), but not necessarily the severity of the reaction. Case history (symptoms, relation to meals, etc.) and clinical examination by the physician are essential for a reliable interpretation of the results.
A negative anti-oyster IgE result (< 0.35 kU/L) indicates that oysters are probably not responsible for the symptoms reported by the person, but it DOES NOT COMPLETELY RULE OUT THIS POSSIBILITY. Both negative and positive results must be interpreted in light of the case history. In more complex cases, the double-blind oral food challenge remains the definitive technique for confirming the presence or absence of an oyster allergy. Unlike milk and egg white allergies, which many children outgrow, the hypersensitivity to oysters and other seafood tends to develop in adulthood and persist for life.