[New aspects in autoantibody diagnosis in collagen diseases]

Distinct, especially non-organ specific autoantibodies are closely associated with connective tissue diseases and in many cases are vital elements of the laboratory diagnostics of these disorders. Their inclusion into the common classification criteria is quite heterogeneous. None of the autoantibodies is 100% specific for a certain disease, and diagnostic specificity is usually reduced when application of the test is broadened and when more sensitive methods are used. In individual patients with scleroderma and/or myositis related diseases, typical autoantibodies usually exclude each other; however, there are characteristical exceptions from that rule. Evidence is accumulating that autoantibodies are detectable early during disease course and often even in preclinical stages. Variations of antibody levels during disease course are different in different systems and in some cases have been shown to correlate with disease activity. Negative results in sensitive screening assays are often essential to exclude a connective tissue disease. Although it has certain drawbacks and is being disputed, the indirect immunofluorescence assay with HEp-2 cells still serves as a standard first step in connective tissue disease-related antibody detection. In case of positive results in this assay, further steps should be performed carefully, considering the signs and symptoms of the suspected disease as well as the immunofluorescence pattern, and being aware of the peculiarities and limitations of the assay methods used.