Suspected allergy: a sequential protocol for testing patients' sera

Sera from 591 patients were examined for total IgE concentration and for reactivity against a panel of seven specific allergens, using the radio-allergosorbent test (RAST). As the total IgE increased, the frequency of positive RAST reactions increased (P less than 0.001); there were more multiple positive RAST reactions (P less than 0.001); and there was a higher grade of RAST reaction (P less than 0.001). However, 12% of patients with normal IgE levels were positive by RAST. From these data a sequential protocol for testing sera of patients with suspected allergy has been developed. Sera should first be tested for total IgE, RAST reactivity to grass pollen and house dust mite. Samples reactive in either assay should be tested with the remaining five discs of the full screen. This protocol reduces unnecessary tests, but allows identification of sera with positive RAST results.