Longitudinal fluctuation of antibodies to extractable nuclear antigens in systemic lupus erythematosus

Objective. To examine the appearance, persistence, and disappearance of anti-extractable nuclear antigen (ENA, Sm, U1-RNP, Ro/SSA, and La/SSB) and anti-native DNA (dsDNA) antibodies during systemic lupus erythematosus (SLE) followup. Methods. One hundred and thirty patients who fulfilled American College of Rheumatology classification criteria for SLE with at least 5 yearly anti-ENA and dsDNA tests between 1987-2002 were retrospectively selected. Four longitudinal antibody data patterns were considered for each antibody: always absent, always present, absent at diagnosis with positive seroconversion, and present at diagnosis with negative seroconversion. Results. Antibodies to Ro/SSA were present in 47%, U1-RNP in 36%, DNA in 32%, Sm in 23%, and La/SSB in 7% of patients. Among patients ever positive for a given autoantibody, the frequency of the "always present" pattern was 52% for anti-Ro/SSA, 38% for U1-RNP, 17% for Sm, 11% for La/SSB, and 9% for DNA antibodies; the frequency of positive seroconversion was 56% for anti-La/SSB, 33% for DNA, 26% for Sm, 21% for U1-RNP, and 15% for Ro/SSA. Time to positive seroconversion varied from 1 to 8 years after diagnosis. Among patients with a positive test at diagnosis the frequency of those remaining positive between the 2nd and 4th year of followup decreased to 39-78%, depending upon autoantibody specificity; between the 5th and 10th years this rate was 20-75%. Antibody data pattern frequency differed significantly among autoantibody specificities except between anti-U1-RNP and Ro/SSA (p = 0.15) and between anti-DNA and Sm antibodies (p = 0.29). Conclusion. The high frequency of longitudinal fluctuation in anti-ENA antibodies suggests that a periodic reappraisal may be appropriate in seronegative patients with a suspect diagnosis of SLE. The clinical significance of such fluctuation deserves future study.