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The positive demonstration of ds-DNA in a particular concentration is a diagnostic criterium for systemic lupus erythematosus. The most commonly used test at present has the disadvantage that radioactively marked substances are required. Thus a test method was developed for the laser nephelometer which is simple and which detects the antigen-antibody complex directly. First measurements on sera from SLE patients showed a good correlation with radioimmuno assay.

Quantitative laser-nephelometric detection of rheumatoid factor, using IgG coated latex particlesSummary: The laser-nephelometric test (Latex RF test) detects rheumatoid factor activity, and is based on immune complex formation between IgG coated latex particles and rheumatoid factor. This test requires little time and gives quantitative results with good precision. The latex nephelometric test and the frequently used agglutination tests (Waaler-Rose, Latex agglutination test) give the same qualitative results. In the quantitative assay higher nephelometric results correlate on average with higher titers in the Waaler-Rose and Latex agglutination test. The high standard deviation could be explained by the fact that other factors (IgG rheumatoid factor, IgG and IgG-IgM immune complexes), in addition to the IgM rheumatoid factor concentration, influence the immune complex formation in vitro.