Skin Prick and Challenge allergy testing remain the “gold standard” in diagnosing allergies. Blood testing for specific IgE antibodies can occasionally give misleading and falsely elevated positive results. For example a number of previously non-allergic people stung by Honey bee’s develop an antibody to a glycoprotein which seems to precipitate multiple unrelated positive allergy RAST test results to many of the common food and inhalant allegens. These blood tests include RAST tests and ImmunoCAP specific IgE allergy tests. It appears that it is a CCD glycoprotein on the actual test reagent or “CAP” that reacts with the person’s blood sample leading to falsely elevated test results which are not clinically relevent. Fortunately there is a new Immuno CAP test that identifies these polysensitised people and they can then be further investigated for possible allergies. The international allergy test company Phadia / Thermofisher now have an specific ImmunoCAP MUXF3 for Bromelain (o214) which identifies those people who may be showing false positive allergy tests. The cardinal feature is a person who reports modest allergy symptoms but has tests results showing they are highly sensitized to numerous unrelated allergens and who appears to be able to normally tolerate exposure to these allergens in day to day life.
Reference: Pevec B, Radulovic Pevec M, Stipic-Markovic A, Batista I. Polysensitisation as a diagnostic problem in a clinical practice: a case report. EAACI Congress, Vienna-Austria. 2006 Jun; Oral Abstract 1038.