2nd order laboratory parameters – depending on the results of the medical history, physical examination, etc. – for differential diagnostic clarification
- Histamine (blood, plasma, urine).
- Diamine oxidase (DAO)* – marker for the diagnosis of histamine intolerance and associated clinical pictures; if DAO deficiency or inhibition is present, the organism cannot break down histamine ingested with food or released from the body’s own cells quickly enough (histamine intolerance).
- Total IgE; allergen-specific IgE (RAST), furthermore the following parameters:
- Tryptase (detection of mast cell involvement) – in allergic reactions (food contact),
- Eosinophil cationic protein (ECP) – suspected allergic diathesis in the allergen-free interval, especially if serum IgE (total IgE) is not elevated).
Type I (immediate type) clinical pictures: Quincke’s edema, urticaria: caused by food allergens.
- Celiac disease serology: transglutaminase antibody (tTG) or endomysium antibody (EMA)/endomysium IgA and transglutaminase IgA.
- Transglutaminase-IgA: sensitivity 74-100%, specificity (probability that actually healthy individuals who do not have the disease in question are also identified as healthy in the test) 78-100%.
- Endomysium antibody (EMA): sensitivity (percentage of diseased patients in whom the disease is detected by use of the test, i.e., a positive test result occurs) 83-100%, specificity 95-100%; there is an association between titer level and degree of villous atrophy
- Selective IgA deficiency (determination of total IgA) must be excluded beforehand (prevalence (disease frequency) 2%); because in the presence of IgA deficiency* endomysium and transglutaminase IgA antibodies may not be detectable.
Further to diamine oxidase determination in plasma.
- DAO activity can be inhibited by substances such as alcohol or drugs (N-acetylcysteine, ambroxol, aminophylline, amitriptyline, chloroquine, clavulanic acid, isoniazid, metamizole, metoclopramide, propafenone, verapamil, and many others) [see also subtheme: “Biogenic Amines – Pharmacological Intolerance]).
- The test for diamine oxidase is controversial in terms of its significance.