Rapid Latex Agglutination Test for Rubella Antibody

John L. Sever, Nancy R. Tzan, Isabel C. Shekarchi, David L. Madden
1983 Journal of Clinical Microbiology  
The latex agglutination card test (Rubascan) for the detection of rubella antibody was compared with the standard hemagglutination inhibition and enzyme-linked immunosorbent assay tests. There was complete agreement with sera which had hemagglutination inhibition titers of .16. Sera with low levels of antibody which were positive in the enzyme-linked immunosorbent assay, however, gave negative latex agglutination results approximately 25% of the time (false negatives), whereas sera which were
more » ... s sera which were negative in the enzyme-linked immunosorbent assay gave false-positive results in about 3% of the cases. The use of capillary "finger stick" plasma instead of venous sera resulted in additional falsenegative latex agglutination tests among patients with very low antibody titers. Because of the simplicity of the method, it should be possible to use this test in physicians' offices and in large immunization campaigns. Care should be taken to become completely familiar with the procedures and reading of the agglutination patterns. Control sera should always be used. Interpretation of results should take into consideration the rates of false-negative and false-positive results noted above. These rates apply to sera with little or no antibody. In particular, negative tests should be confirmed with more specific methods in critical cases, such as pregnant women exposed to rubella or women of childbearing age who are being considered for immunization. There was no problem with the latex agglutination findings for sera with higher titers. Since results are available in 8 min, physicians should be able to counsel their patients rapidly and immunize, if necessary, while the patient is still present. More than 20 kits are now available for the detection of rubella antibody (1, 3). Most of the kits use the hemagglutination inhibition (HI) method. Some, however, employ indirect hemagglutination, enzyme-linked immunosorbent assay (ELISA) or immunofluorescence. Most of these tests require 1 to 2 days for completion and considerable technical ability and equipment for performing the test properly. Recently, a new, simple latex agglutination (LA) test (Rubascan) became available for the rapid detection of rubella antibody. This method was evaluated and compared with the HI and ELISA tests for rubella. MATERIALS AND METHODS Serum specimens. The serum specimens used for this study were selected from a large panel of specimens which have been studied in our laboratory for rubella antibody. Because of the importance of distinguishing samples with no detectable rubella antibody from those with low levels of antibody, 76 of the 152 sera used for this study were known to have no detectable HI antibody to rubella at a 1:8 dilution. Twenty-three sera were included which had only a titer of 1:8 by the HI method. The remaining sera had various levels of antibody. These sera were also tested by the ELISA method for rubella antibody detection (2). HI test. All of the sera were retested with our standard HI test (4). Briefly, this test employed pretreatment of the sera with Kaolin and the use of 1-dayold chicken cells for hemagglutination. ELISA test. All sera were tested by the ELISA method, and the level of antibody was quantitated as previously described (2) . LA test. The LA kit called Rubascan, marketed by Hynson, Westcott and Dunning, Baltimore, Md., was used for these tests. The tests involved the mixing of 1 drop of undiluted serum (25 RI) with 1 drop of the prepared latex antigen (latex particles coated with rubella virus antigen), approximately 15 RI. The mixing was done with a plastic spatula on a marked circle on a firm, dark card. The card was then rotated for 8 min on a mechanical platform with a plastic cover and wet sponge to minimize evaporation. At the end of 8 min, the test was read and reported as positive if there was evidence of agglutination of the latex (Fig. 1) . Venous serum compared with capillary "finger stick" heparinized plasma. Venous serum samples and simultaneous finger stick heparinized plasma samples were 52 on March 22, 2020 by guest
doi:10.1128/jcm.17.1.52-54.1983 fatcat:pnjz53ragnb5nmloqitssrakeu