Assessment of Deoxyribonuclease Activity in Serum Samples of Patients With Systemic Lupus Erythematosus:...

We report the improvement of previously described method for determining deoxyribonuclease (DNase) activity in serum samples that uses a fluorescently labeled DNA fragment as a substrate METHODS: Activity of serum DNase was analyzed in 31 patients with systemic lupus erythematosus (SLE) and 13 healthy individuals by fluoresence-based method and ELISA test RESULTS: We found a mean decrease in DNase activity between cases and controls of 12.46% measured by the fluoresence-based method and of 12.21% measured by ELISA method. High level of positive correlation between two methods for DNase activity was observed: P < 0.001 and Pearson correlation coefficient 0.740. Decreased DNase activity was found in 25 of 31 SLE patients (81%) by fluoresence-based method and in 24 of 31 SLE patients (77%) by ELISA test. We also observed the significant positive correlation between titer of anti-dsDNA antibodies and DNase activity measured by both methods (P < 0.05).

The key improvement is the use of internal control in the fluorescence-based method, which diminishes the influence of technical errors on the obtained results and increases reliability of the assay. This improved fluorescence-based method, with additional validation, may provide an alternative to more expensive and time-consuming conventional methods, such as ELISA.