Diagnostic tests in ragweed hay fever. A comparison of direct skin tests, IgE antibody measurements, and basophil histamine release

In 87 patients with both spring and fall hay fever symptoms the radioallergosorbent test (RAST) technique for specific IgE antibodies to ragweed was compared with basophil histamine release and direct intradermal skin testing by the threshold dilution technique. The three techniques gave good agreement except with the leastsensitive patients, some of whom had a positive skin test but undetectable histamine release or IgE antibodies. Twenty-one patients who were highly sensitive to ragweed as measured by all three techniques were followed without specific immunotherapy. There was significant agreement between the level of positivity of all three tests and the symptom index obtained during the ragweed season. In 14 of the 21 patients there was a significant correlation between daily ragweed pollen counts and daily symptom indexes during the season. On the other hand, among the 16 least-sensitive patients (as judged by histamine release) the correlation between daily ragweed pollen counts and symptom indexes was significant in only 3 patients. Other significant allergens could not be identified in the latter group, and the cause of their symptoms is not clearly identified but appears not to be ragweed. The RAST is a quantitative technique that gives diagnostically useful information in ragweed hay fever, although not significantly different from basophil histamine release or carefully performed skin testing. The convenience to the patient may, however, offer a noticeable advantage.