Comparison of immunofluorescence investigations and a new anti-DNA-antibody radioimmunoassay for the diagnosis of connective tissue diseases

The procedure of determining the anti-DNA antibody activity is simplified by high-molecular double strand DNA labelled with 125I. Cases of suspected connective tissue disease should first be examined by immunofluorescence microscopy, since this method can detect a wider spectrum of diseases with similar symptoms. For a differential diagnosis of SLE, the anti-DNA antibody activity is then investigated by a radioimmunoassay. When assessing the antibody activity, the following criteria should be kept in mind: - Findings of less than 10 units/ml serum do not indicate pathological changes, - Higher antibody activities up to 35 units/ml serum may occur in SLE patients but are also possible in other ANA positive diseases with similar symptoms, - Activities over 35 units/ml serum are nearly always a sign of SLE. (orig./GSE)