The radioallergosorbent test (RAST) was applied for quantitative estimation of IgE antibodies to various common allergens. The results could be expressed in per mille of a reference serum containing IgE antibodies to birch allergen. Since the allergen extracts vary considerably both on a quantitative and qualitative basis, the results cannot, with few exceptions, be compared between different allergens. However, for each type of allergen the results can be compared between samples obtained from different individuals or at different times. Birch and dandelion allergen extracts were found to be potent and give rise to allergen excess in the systems used. A comparison between these two allergens showed that a group of allergic children had on the average approx. 15 times more circulating IgE antibodies to birch than to dandelion allergen.

The radioallergosorbent test (RAST) has been used for in vitro diagnosis of allergy in a selected group of children with asthma and allergic rhinoconjunctivitis. The results were compared with those of provocation tests and also with the results of skin tests. Where the results of RAST and the provocation tests differed, repeated tests were performed, initially in vitro and secondly in vivo. Selected commercial allergens of good quality were used and, for the most part, the same allergen batches were used in RAST, in the provocation tests and in the skin tests. A 76% correlation between RAST and provocation tests was found on preliminary investigation before divergent results were repeated. This degree of correlation is similar to that obtained previously in unselected patients using RAST as a part of the routine diagnostic. On repeated examination, agreement was obtained in an additional 16% of the cases. The major part of the improvement (13%) was due to conversion of preliminary RAST results from negative to positive in children with positive provocation tests. To a minor extent, the improvement was due to the fact that, in some children with positive RAST, negative provocation tests became positive when repeated. Finally, in one case an originally positive RAST in a child with a negative provocation test was found to be negative on re-examination. Comparing the final revised results of RAST and provocation tests there were no cases where a negative provocation test was combined with a positive RAST. Nearly all the children with positive provocation tests in spite of a negative RAST were shown to have low degree allergy. Although circulating reaginic antibodies are not always present, it seems that, on repeated investigations, the great majority of children with asthma and hay fever can be shown to have such antibodies even though the serum concentration may be low or very low. In doubtful cases repeated RAST examinations may be of value.

The reaginic activity in serum from pollen-allergic children, determined by the radioallergosorbent test (RAST) was followed before, during and after the pollen season. In addition, the serum concentration of IgE was examined. The investigation included both untreated children and children treated by inhalations of disodium cromoglycate for pollen-induced asthma. Typical seasonal variations of IgE antibodies and pollen allergens, as well as total IgE, were found in the majority of the children. In general, changes of specific antibodies were considerably more pronounced than those of total IgE. The serological course was characterised by a rapid increase in reaginic activity during the pollen season. In some patients reagins could not be determined by the RAST technique before the season. However, reagins were found both during and after the season. In 1 patient, circulating reagins were found during, but not after, the pollen season. Very favourable results were obtained following treatment with disodium cromoglycate. Treated patients showed pronounced serological changes of a type similar to those observed in untreated cases, despite absent or insignificant asthma symptoms. In a group of patients, allergic to birch pollen, that was treated with disodium cromoglycate the average increase in the birch reaginic serum level was almost twice as high as that found in untreated patients allergic to birch pollen.

In 20 children with symptoms of asthma or allergic rhinoconjunctivitis the serum concentrations of IgE antibodies (reagins) and of total IgE were followed during and after rush desensitization. The reaginic activity in serum was determined by the radioallergosorbent technique (RAST). In the majority of children an increase was found 2–4 weeks after the start of the treatment both of the IgE antibodies and of the total concentration of IgE. In some cases this increase was very pronounced. Usually the increase of IgE antibodies was more pronounced than that of total IgE. The reaginic increase was often but not always observed during the first days of treatment. The quantitative changes were most varying, both in the group and in the same individual concerning IgE antibodies to different allergens.