Phadia’s F40 test is used to detect blood levels of the IgE (antibodies) responsible for allergic reactions to tuna. People with allergies to tuna may have cross allergies with other fish (cod, hake, mackerel, etc.) but, unless there is a true double allergy, they will not necessarily be allergic to crustaceans and other seafood. The interpretation chart accompanying the result expresses the probability of an allergic reaction to tuna (and possibly other fish), but not necessarily the severity of the reaction. Case history (symptoms, relation to fish consumption, etc.) and clinical examination by the physician are essential for a reliable interpretation of the results.
A negative anti-tuna IgE result (< 0.35 kU/L) indicates that tuna is 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. The double-blind oral food challenge remains the definitive technique for confirming the presence or absence of a tuna allergy. Unlike milk and egg white allergies, the hypersensitivity to tuna and other fish often develops in adulthood and tends to persist for life.