Absence of an association between anti-Ro antibodies and prolonged QTc interval in systemic sclerosis: a multicenter study of 689 patients.

Objective: To examine the association between anti-Ro antibodies, namely anti-Ro60/SS-A and anti-Ro52/TRIM21, together and separately, and a prolonged QT interval corrected for heart rate (QTc) in systemic sclerosis (SSc) patients.

Methods: A total of 689 SSc patients enrolled in a multicenter cohort study underwent a 12-lead resting EKG at baseline. The QTc interval was measured, and a QTc ≥ 440ms was considered prolonged. Detailed clinical data and sera of these patients were collected and positivity for anti-Ro60/SS-A and anti-Ro52/TRIM21 antibodies was determined using an addressable laser bead immunoassay (ALBIA).

Results: QTc prolongation was common in this SSc cohort (25%). In a univariate analysis, Ro antibodies, together or separately, were not associated with prolongation of the QTc interval [mean difference in QTc in anti-Ro antibody positive versus negative subjects was -2.2ms (p = 0.5748), in anti-Ro60/SS-A antibody positive versus negative subjects was 1.3ms (p = 0.8616), and in anti-Ro52/TRIM21 antibody positive versus negative subjects was -3.3ms (p = 0.4106)]. In a multivariate logistic regression analysis adjusting for possible confounders, there was no association between prolonged QTc and anti-Ro antibodies [odds ratio (OR) = 0.74, 95% confidence interval (CI): 0.45, 1.22], anti-Ro60/SS-A antibodies (OR = 1.57, 95% CI: 0.72, 3.41), and anti-Ro52/TRIM21 antibodies (OR = 0.76, 95% CI: 0.46, 1.26). However, in both univariate and multivariate analyses, QTc prolongation was associated with longer disease duration, greater disease severity, and the presence of anti-RNA polymerase III antibodies.

Conclusions: QTc prolongation is common in SSc, although anti-Ro antibodies do not seem to be associated with it as is the case in systemic lupus erythematosus. The reasons for this difference as well as the cause of abnormalities in cardiac repolarization in SSc will require additional studies.