Figure 114

Algorithm for analysis of antinuclear antibodies (ANA) in systemic lupus erythematosus. To demonstrate the presence of antinuclear antibodies the ANA test is used as a screening procedure. Details of this ANA test and the different ANA patterns are given in Figure 11-5. A positive ANA test result indicates the presence of antinuclear antibodies. Although the pattern of ANA can give an indication about the specificity of the antinuclear antibody, additional tests are needed to define this specificity. Antibody specificity to double-stranded DNA (dsDNA) can be identified by the Crithidia assay (Fig. 11-6), in which a single-celled organism is used that has purely dsDNA in the kinetoplast. When this test result is positive, the titer of anti-dsDNA antibodies can be determined using the Farr assay (Fig. 11-7). When these anti-dsDNA test results are negative, ANA positivity is most likely caused by antibodies directed against nuclear proteins. Autoantibodies can be analyzed by the Western blot test on nuclear extracts (Fig. 11-8). The advantage of this technique over the Ouchterlony technique using extractable nuclear antigens (ENA), is that the Western blot test allows identification of a large number of autoantibody specificities in one test, although both tests do not completely overlap.

0 0

Post a comment