Diagnosis of postnatally acquired rubella by use of three enzyme-linked immunosorbent assays for specific immunoglobulins G and M and single radial hemolysis for specific immunoglobulin G.

Three commercial indirect enzyme-linked immunosorbent assays (ELISAs) (RUBELISA, Enzygnost-Rubella, and Rubazyme) and a commercial single radial hemolysis (SRH) test (Rubazone) were evaluated for the diagnosis of acute rubella by testing 41 acute- (less than 7 days postonset) and convalescent-phase (8 to 82 days postonset) serum pairs from cases of rubella previously confirmed by significant change in the hemagglutination inhibition test titer. Specificity was tested by using 10 acute- and convalescent-phase serum samples from patients with rash not confirmed as rubella (control group). In testing for rubella-specific immunoglobulin G (IgG) antibody, Enzygnost-Rubella and Rubazyme confirmed infection in 40 and RUBELISA in 39 of the 41 proven rubella patients. For one patient all three ELISAs failed to show a significant titer rise. No false-positive diagnoses occurred in the control group, although a suspected infection was shown by Rubazyme in one patient. No specific IgM could be detected in this case. Single radial hemolysis confirmed infection in 39 of the 41 proven rubella patients, and one false-positive diagnosis occurred in the control group patients. Of the 43 convalescent-phase serum samples, rubella-specific IgM was detected in 42 by Enzygnost-Rubella, in 41 by RUBELISA M, and in 39 by Rubazyme-M. For a rapid diagnosis with acute-phase sera, specific IgM detection by ELISA was most reliable in hemagglutination inhibition test-positive sera; of 18 such serum samples IgM was shown in 15 by Enzygnost-Rubella, in 13 by RUBELISA M, and in 11 by Rubazyme-M. False-positive specific IgM results were shown by Rubazyme-M in two serum samples from one patient in the control group. These serum samples were negative with the other two ELISA methods.