Capacity to predict a recurrence of lupus erythematosus using double-stranded anti-DNA antibodies and Farr technique

Patients with inactive systemic lupus erythematosus (SLE) and elevated high affinity double-stranded anti-DNA antibodies (anti-dsDNA), measured using Farr technique, would have a risk of relapse that fluctuates between 40 to 80% according to different series. To study the association between anti-dsDNA levels measured using Farr technique and disease activity and their predictive capacity for relapses. Anti-dsDNA antibodies were measured according to Farr method in 60 healthy subjects, 69 patients with other connective tissue diseases and in 120 patients with SLE. Farr positive were considered those individuals with anti-dsDNA levels over 10.4 IU/ml. Disease activity, assessed using MEX-SLEDAI score was related with anti-dsDNA levels in 101 patients. Forty seven patients with inactive disease were followed for 17 +/- 14 months. Anti-dsDNA levels were 3 +/- 2.5 IU/ml (range 1-26) in subjects without LED, and 127 +/- 500 IU/ml (range 1-5280) in patients with LED. Sixty subjects had an active SLE and 43 (72%) were Farr positive; in 41 the disease was inactive and 13 (32%) were Farr positive (p < 0.001), OR 5.45. Twelve of the 47 followed patients had a relapse and 10 (83%) were Farr positive. Of those that did not have a relapse, 13 (37%) were Farr positive (p < 0.02, RR 5.22). Six of 15 patients that were followed for more than on year (40%), were Farr positive. Elevated anti-dsDNA antibodies measured using Farr technique in patients with inactive generalised lupus erythematosus, predicted the risk of relapse. However less than half of patients with inactive disease and elevated Farr relapsed in a period of one year. The need to treat patients with inactive SLE and positive Farr should therefore be considered debatable.