Measurement of plasma DNA by a physiochemical method: relevance in SLE.

Plasma DNA has been measured by a new physiochemical approach based on fluorimetric analysis of phenol extracted nucleic acids electrophoresed on polyacrylamide gels. This method is specific for native double-stranded DNA of molecular weight greater than 5 x 10(6). The use of plasma rigorously freed of leucocytes is essential to prevent falsely high values. When such precautions are taken levels seldom exceed 50 ng/ml in normal individuals. Plasma DNA was assayed in 107 samples from 47 patients with both active and inactive systemic lupus erythematosus. In direct contrast to several previous reports no significant increase of plasma DNA was found.