Abstract
OBJECTIVES: Systemic extraglandular involvement in SS has been reported in one-third of patients but may be more frequent. We aimed to evaluate systemic disease prevalence at baseline and throughout follow-up and find its predictors. METHODS: We conducted a retrospective cohort study including SS patients followed in a tertiary centre. The cumulative EULAR SS disease activity index (ESSDAI) was calculated by adding each domain's maximum score throughout follow-up. We identified independent predictors of systemic involvement (ESSDAI ≥1 at baseline and/or follow-up) through logistic regression modelling. A survival analysis was conducted to identify predictors of new/worsening ESSDAI domains. RESULTS: A total of 216 patients were included, most of whom had systemic involvement (86%), frequently at diagnosis (76%). Biological (53%) and articular ESSDAI domains (44%) were most commonly involved, but all were affected at least once. Around half of the patients with baseline systemic disease developed an additional/worsening domain throughout follow-up. Although most patients had low disease activity at baseline, 60% eventually reached moderately active disease. Younger age at diagnosis [odds ratio (OR) 0.95 (95% CI 0.91, 0.99)], a positive minor salivary gland biopsy [OR 4.08 (95% CI 1.40, 11.86)] and RF [OR 4.67 (95% CI 1.52, 14.33)] were independent predictors of systemic involvement. Patients with baseline constitutional involvement [hazard ratio (HR) 2.23 (95% CI 1.13, 4.40)] and RF [HR 1.89 (95% CI 1.20, 3.00)] were more likely to develop new/worsening systemic disease activity. CONCLUSION: Systemic involvement is seen in most SS patients. Younger and RF and salivary gland biopsy-positive patients are at higher risk of systemic disease. Around half of patients with systemic involvement experienced aggravated disease over time, especially those with constitutional involvement or RF.