An increasing number of patients are suffering from allergic diseases such as rhinoconjunctivitis,
atopic eczema, uticaria,
anaphylaxis, and food and
drug allergies. Although it is possible to measure a multitude of
allergen-specific
IgE antibodies by radio or
enzyme immunoassays in the patients' blood, these tests are expensive, time-consuming, and usually need a rather high volume of
reagent solutions (
allergens and blood).
Protein microarrays offer the possibility to circumvent these limitations. The described in vitro
allergy testing system is based on microscopic glass slides activated with glycidyloxypropyl-
trimethoxysilane.
Allergen solutions (
allergen extracts and/or purified
allergens; approximately 10 nL) are printed on the activated glass surface with a piezoelectric
spotting machine. The
protein components of the
allergen solutions are immobilized on the modified glass surface via hydrophobic interaction and/ or covalent binding. After a blocking step, the slides are incubated with the respective diluted serum sample (approximately 25 microL serum required) and bound
IgE antibodies are detected with a secondary
horseradish peroxidase (HRP) labelled anti-human-
IgE antibody via chemiluminescence. The measurement can be performed automatically with the so called PASA system. Test results are directly visualized with a CCD-camera. Analytical and clinical data have shown that the microarray-based test format offers significant advantages in time and costs compared with traditional test formats. The described
allergen microarray demonstrated a sufficient qualitative reproducibility and enabled the distinction between allergic and non-allergic patients. Detection limits of 0.35 kU/L (r Bet v1), 0.16 kU/L (PLA2), 1.9 kU/L (Der p1), and 41 kU/L (total
IgE) were achieved.