Determination of immune status in patients with low antibody titers for rubella virus

Three assays for detection of rubella antibodies, Rubella G (fluorescence immunoassay [FIA]), Rubacell (passive hemagglutination), and Rubaquick (passive hemagglutination with rotation), were compared with hemagglutination inhibition. A total of 100 serum specimens were selected, 68 of which had an FIA value of less than or equal to 25. On initial testing, among the four tests, there was agreement for 88 specimens for assignment of rubella immune status. On repeat testing, all the results agreed by the hemagglutination inhibition, passive hemagglutination, and passive hemagglutination rotation methods, and only one discrepant specimen remained by FIA.