Diagnosis of postnatal rubella by the enzyme-linked immunosorbent assay for rubella IgM and IgG antibodies.

A semi-automated enzyme-linked immunosorbent assay (ELISA) was established for the detection of rubella IgM antibodies in non-fractionated sera. A cut-off level between rubella IgM positive and negative sera was determined by a study of sera without rheumatoid factor from 200 blood donors. Testing of 12 donor sera containing rheumatoid factor showed that 5 sera gave a positive result in the rubella IgM assay. Rubella IgM antibodies were quantified by ELISA in a study of 214 serial serum specimens drawn from 16 patients with rubella during a period of up to 10 years after the infection. Peak values of the IgM antibodies were reached approximately 8 days after onset of the rash, and the persistence of the IgM antibodies ranged from 17-90 days, with the exception of one patient with a prolonged IgM response. The rubella IgG antibodies increased slowly after the rash and reached maximum levels about 50-120 days, after which a monor decrease was observed. The results of the present study indicate that ELISA is suitable as a routine procedure for the serodiagnosis of recent rubella.