radioallergosorbent test (RAST) /rā′dē·ō′alur′gōsôr″bənt/ [L, radius + Gk, allos, other, ergein, to work; L, absorbere, to swallow] , a test in which a technique of radioimmunoassay is used to identify and quantify IgE in serum that has been mixed with any of 45 known allergens. If an atopic allergy to a substance exists, an antigen-antibody reaction occurs with characteristic conjugation and clumping. The test is an in vitro method of demonstrating allergic reactions. Compare patch test, Prausnitz-Küstner test.
