Free DNA in the serum of rheumatoid arthritis patients

Seventy patients with classical or definite rheumatoid arthritis (RA) were studied in an attempt to correlate the serum levels of free DNA with other features. In 26 patients (37%), levels of DNA ranging from 100-540 ng/ml, with a mean of 187 ng/ml, were found. In additional seven patients with a mean of 257 ng/ml, low levels of anti-DNA-antibody were observed. The remaining of 37 patients (53%) had levels of 0-80 ng/ml in their sera, with a mean of 39 ng/ml. All three groups differed significantly (p less than 0.01) from the control group of 61 healthy individuals, who had levels of 0-80 ng/ml with a mean of 13 ng/ml. The high levels of free DNA were commonly found in patients with more severe symptoms who had active RA for less than 10 years, whereas patients with longer duration of disease showed lower levels of DNA. In addition, elevated DNA levels were found more commonly in patients seronegative for rheumatoid factor (RF). Other clinical features did not show significant differences among these patients. The implications of these findings to the pathogenesis of the disease are discussed.