Evaluation of the solid-phase radioimmunoassay for diagnosis of St. Louis encephalitis infection in humans.

Since the use of highly purified viral proteins in the solid-phase radioimmunoassay (SPRIA) procedure is not practical for routine diagnostic serology, the procedure was adapted for use with the crude antigens now commonly used to diagnose St. Louis encephalitis (SLE) virus infections. SLE and various other alpha- and flavivirus antigens were tested by both the SPRIA procedure and conventional serological methods. Standards were established for use of the crude antigens in the SPRIA procedure. Reproducibility of the procedure was similar to that of conventional tests. The SPRIA procedure specifically differentiated SLE from clinically similar alphaviruses, but did not differentiate SLE from related flaviviruses very well. SPRIA diagnosis of SLE infections by the immunoglobulin G response in paired sera was good. Generally, the crude antigen SPRIA procedure was as sensitive as the conventional serological tests, but not as specific.