The Use of RDE to Improve the Sensitivity of the Hemagglutination-Inhibition Test for the Serologic Diagnosis of Influenza

Abstract

To aid in the selection of a serologic procedure best suited for the measurement of changes in the levels of influenza antibodies in serum specimens collected from individuals at six month intervals, paired sera from 58 patients with influenza and other acute respiratory illnesses were tested by the complement-fixation and hemagglutination-inhibition techniques employing PR8, FM1, Lee and 1233 influenza virus antigens. By using the complement-fixation test for reference, it was shown that destruction of heat stable (62°C) non-specific inhibitor by RDE increased the sensitivity and reliability of the hemagglutination-inhibition test in 22% of the cases. RDE did not alter serum inhibitor levels against 1233 virus. RDE affected a greater reduction of inhibitor active against Lee antigen than of inhibitor against PR8 or FM1 antigens. With proper antigens, the hemagglutination-inhibition test on RDE treated sera is as sensitive as the complement-fixation test with virus antigen. It has been shown by others that use of soluble antigen increases the sensitivity of the complement-fixation test, but the antibody elevation measured is transient. It is believed that the hemagglutination-inhibition test using RDE is the method of choice for measuring changes in the level of influenza antibodies in serum specimens collected at wide intervals.