The value of tests for antibodies to DNA in monitoring the clinical course of SLE. A long-term study using the Farr test and the DNA counterimmunoelectrophoretic method.

Serial serum samples from fifteen patients with SLE, taken over periods varying from 6 months to 6 years, were tested for DNA binding capacity, DNA electroprecipitins (DNA-EP) and C'3 level to assess the value of these investigations in reflecting clinical disease activity. Patients with renal involvement showed a good correlation between high levels of DNA binding, low serum C'3 and disease activity and typically, their DNA-EP was negative. By contrast, patients without renal involvement in whom vasculitis was prominent, showed a poor correlation of DNA binding capacity to changes in the state of their disease although the DNA-EP test was persistently positive. It was also apparent that both the DNA-BC and C'3 can show marked variation in response to alterations in treatment without accompanying clinical change. Although these serological tests, particularly the DNA binding capacity are of recognized value in the diagnosis of SLE, they serve most usefully as guides to long-term management when they can be related to the clinical pattern of the disease.