[The diagnostic value of antinuclear antibodies]

In this review we focus on the diagnostic importance of antinuclear antibodies (ANA), the biological function of the relevant autoantigens and on some methodological questions regarding the detection of ANA. The qualitative and quantitative evaluation of ANA has improved significantly in recent years with the introduction of several new test kits. A precondition for the rational use of those assays is knowledge of the diagnostic validity of the detected ANA with regard to the method used. ANA are autoantibodies that react with nucleic acids, protein-nucleic acid complexes and proteins of nuclei. The reasons for their in vivo production are unknown. ANA characterize several of the so-called connective tissue autoimmune diseases and their subtypes, either alone or in typical combinations. They differ significantly with regard to their prevalence and thus in their diagnostic validity. Specificity and prevalence do not correlate. ANA are not markers of disease activity except for antibodies against dsDNA. ANA levels can be interpreted correctly only in connection with clinical symptoms and other laboratory findings.