Autoantibodies to Ro(SS-A) may recognize two different polypeptides, of 52 kDa and 60 kDa, respectively. We used an ELISA with purified human recombinant antigens to conduct a detailed analysis of the specificities of anti-Ro(SS-A) antibodies from 170 patients with definite diagnoses (systemic lupus erythematosus [SLE], n = 55; primary Sjögren's syndrome [PSS], n = 39; systemic sclerosis, n = 9; rheumatoid arthritis [RA], n = 10) or undifferentiated connective tissue disease (UCTD, n = 57). Most of the patients with SLE or PSS had both anti-52 kDa and -60 antibodies; isolated anti-60 kDa antibodies were found in 13% of the SLE patients and in none of the PSS patients, whereas high titers of anti-52 kDa were more common in the PSS than in the SLE patients. In the UCTD patients, the anti-Ro(SS-A) profile showed no significant correlations with clinical features but was associated with the clinical outcome. Over the mean follow-up of five years, definite SLE developed in four of the five UCTD patients with isolated anti-60 kDa vs only one of the remaining 52 patients (P < 0.0001); progression to PSS was seen in seven of the 34 patients with both anti-52 kDa and anti-60 kDa vs none of the remaining 23 patients (P = 0.03); none of the 12 patients with isolated anti-52 kDa developed a definite connective tissue disease.
Conclusion: Our study suggests that analysis of anti-Ro(SS-A) specificity may provide useful information for predicting the course of UCTD.