Predictive capacity of double stranded anti DNA antibodies for relapses inpatients with inactive systemic lupus erythematosus

Background: Patients with inactive systemic lupus erythematosus (SLE) and e levated high affinity double-stranded anti-DNA antibodies (anti-dsDNA), mea sured using Farr technique, would have a risk of relapse that fluctuates be tween 40 to 80% according to different series. Aim: To study the associatio n between anti-dsDNA levels measured using Farr technique and disease activ ity and their predictive capacity for relapses. Material and methods: Anti- dsDNA antibodies were measured according to Farr method in 60 healthy subje cts, 69 patients with other connective tissue diseases and in 120 patients with SLE. Farr positive were considered those individuals with anti-dsDNA l evels over 10.4 IU/ml. Disease activity, assessed using MEXSLEDAI score was related with anti-dsDNA levels in 101 patients. Forty seven patients with inactive disease were followed for 17+/-14 months. Results: Anti-dsDNA leve ls were 3+/-2.5 IU/ml (range 1-26) in subjects without LED, and 127+/-500 I U/ml (range 1-5280) in patients with LED. Sixty subjects had all 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 patient s 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 patien ts that were followed for more than on year (40%), were Farr positive. Conc lusions: Elevated anti-dsDNA antibodies measured using Farr technique on pa tients with inactive generalised lupus erythematosus, predicted the risk of relapse. However less than half of patients with inactive disease and elev ated Farr relapsed in a period of one year. The need to treat patients with inactive SLE and positive Farr should therefore be considered debatable.