To examine whether anti-Ro/SSA antibodies are associated with an increased risk of corrected QT (QTc) prolongation, and to study the stability of this relationship over time.
Patients fulfilling the American College of Rheumatology (ACR) criteria for systemic lupus erythematosus (SLE) were invited to undergo a 12-lead resting electrocardiogram (EKG) in the pilot phase of our project, performed between February 2002 and March 2005. The same study population was used to perform a second similar analysis with a larger sample between April 2005 and May 2007. Multivariate logistic regression models were fit to estimate the cross-sectional association between anti-Ro/SSA and other demographic and clinical variables on QTc prolongation. The other potentially associated factors examined included age, sex, disease duration, lupus activity (Systemic Lupus Erythematosus Disease Activity Index 2000 update), damage (Systemic Lupus International Collaborating Clinics/ACR Damage Index), potassium and magnesium levels, and medications with the potential to prolong the QTc interval.
Cross-sectional analysis of the pilot data (n = 150 patients) showed an association of prolonged QTc with the presence of anti-Ro/SSA (adjusted odds ratio [OR] 12.6; 95% confidence interval [95% CI] 2.3, 70.7). In the second larger study (n = 278), the association was replicated, with a narrower 95% CI (adjusted OR 5.1; 95% CI 1.5, 17.4). In the 118 patients with 2 EKG assessments, the results were consistent over time.
Anti-Ro/SSA was associated with QTc prolongation in both our pilot data and a larger SLE cohort sample. Patients positive for anti-Ro/SSA may benefit from EKG testing and appropriate counseling should be considered for those identified with QTc prolongation.