[Determination of specific IgE serum antibodies using the Radio-Allergo-Sorbent-Test (RAST) and its significance for the diagnosis of atopic allergy].

The Radio Allergo Sorbent Test (Phadebas-RAST) is a recently developed radioimmunological in-vitro test for determining IgE specific serum antibodies in reaginic allergy. The overall correspondence between RAST and skin tests in 1,128 tests with a total of 19 allergens was 70.2%. The agreement between positive RAST and skin tests was 22.1%. In instances of disagreement the combination of a positive skin test and a negative RAST was much more frequent (24.1%) than the reverse (5,7%). The agreement between RAST and skin tests was 94.5% for cat epithelium, 89.3% for egg white, 86.2% for timothy pollen, 84.2% for milk, 80.3% for mite Dermatophagoides pteronyssinus, 78.8% for birch pollen, 71.9% for dog epithelium, 67.7% for horse dandruff, 57.3% for moulds and only 40.3% for house dust. Positive RAST results for atopic patients with respiratory allergy usually indicate a clinically relevant sensitization (positive case history or positive provocation test), while negative results do not rule out the possibility of significant sensitization. Circulating reagins were detected in 9.4% of the mite and 12.7% of the mould RAST, although the skin tests were negative. The greatest discrepancy between RAST and inhalation test results occurred with house dust (47% agreement, only 12% positive correlation). The RAST was negative in 53% of the cases with positive provocation tests. The first step in the diagnosis of allergy is still a thorough case history combined with careful prick and intracutaneous testing. When the case history and skin tests are in disagreement, RAST may be helpful as a supplementary test. In addition, the RAST may be useful in clarifying cases in which the patient is on continuous steroid or antihistamine therapy, as well as for children who are frightened of skin tests. If house dust asthma is suspected, it is advisable in all but a few instances to utilize the bronchial provocation test to confirm the diagnosis and for initiation of specific desensitization.