Phadia’s F2 test is used to detect blood levels of the IgE (antibodies) responsible for allergic reactions to cow’s milk. Milk contains more than 30 different proteins, all of which are potential allergens. The major proteins, however, are casein and beta-lactoglobulin. The interpretation chart accompanying the result expresses the probability of an allergic reaction to cow’s milk, but not necessarily the severity of the reaction. Case history (symptoms, relation to meals, snacks, etc.) and clinical examination by the physician are essential for a reliable interpretation of the results.
A negative anti-cow milk IgE result (< 0.35 kU/L) indicates that cow’s milk is probably not responsible for the reported symptoms, but, especially in young children, it DOES NOT COMPLETELY RULE OUT THIS POSSIBILITY. All negative and positive results must be interpreted in light of the case history. There are no specific IgE levels that can be used to predict a severe reaction to milk. The double-blind oral food challenge remains the definitive technique for confirming a food allergy. Tracking specific IgE levels over time can be useful in determining the age when cow’s milk can be reintroduced. In some cases, testing for IgE against specific components of cow’s milk (casein, alpha-lactalbumin, beta-lactoglobulin) may be useful.