The F13-Peanut test is used to detect blood levels of the immunoglobulin E (IgE) responsible for allergic reactions to peanuts. This test detects IgE antibodies reacting with whole peanut extracts using the Immunocap© technique. Test results are expressed in kilounits of IgE per litre of blood (kU/L). The interpretation chart accompanying the result expresses the probability of an allergic reaction to peanuts (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. The double-blind oral food challenge (administering peanuts under close medical supervision) remains the definitive technique for confirming a food allergy in less obvious cases.
A negative anti-peanut IgE result (< 0.35 kU/L) indicates that peanuts are probably not responsible for the symptoms reported by the patient, but it DOES NOT COMPLETELY RULE OUT THIS POSSIBILITY. A result above 15 kU/L indicates a high probability (> 95%) of an allergic reaction to peanuts, with the severity of it (from benign to dangerous) depending, among other things, on the nature of the peanut components responsible for the allergy involved. More specific tests (molecular allergens) can identify the nature of the components involved. The presence of anti Ara h1, anti Ara h2 and anti Ara h3 IgE is consistent with a dangerous peanut allergy, and their presence confirms the diagnosis without using the more definitive oral food challenge.