Salivary gland ultrasonographic abnormalities in systemic lupus erythematosus versus rheumatoid arthritis: a comparative cross-sectional study using OMERACT scoring.

Abstract

Objective: To compare the prevalence and patterns of salivary gland ultrasonographic (SGUS) abnormalities in patients with Systemic Lupus Erythematosus (SLE) and Rheumatoid Arthritis (RA) using the OMERACT scoring system, and to investigate their associations with clinical manifestations, serological markers, and patient-reported dryness.

Methods: This cross-sectional study enrolled 70 patients (35 SLE fulfilling ACR/EULAR 2019 criteria; 35 RA fulfilling ACR/EULAR 2010 criteria) and 30 healthy controls. Primary outcome was SGUS positivity rate (OMERACT score ≥ 2 in any gland or ≥ 4 total). Secondary outcomes included individual gland grading, Power Doppler signals, and ESSPRI dryness burden. Participants underwent comprehensive assessment including disease activity scores (SLEDAI-2K for SLE, DAS28-ESR for RA), anti-Ro/anti-La antibodies, and bilateral salivary gland ultrasonography. Intra-observer reliability was assessed on 15% of scans (ICC = 0.89). Multivariable logistic regression adjusted for age, disease duration, and CRP. Primary outcome significance was set at p < 0.05; secondary outcomes were interpreted with correction for multiple comparisons (Bonferroni-adjusted threshold, p < 0.007).

Results: SLE patients were younger (33.08 ± 10.84 vs 43.82 ± 8.95 years, p = 0.001) with numerically shorter disease duration (6.72 ± 7.25 vs 10.58 ± 9.28 years, p = 0.056). Unadjusted SGUS positivity was similar (SLE 62.8% vs RA 57.1%, p = 0.62), both exceeding controls (13.3%, p < 0.001). After adjusting for age, disease duration, and CRP, the association remained non-significant (OR = 1.26, 95% CI 0.48-3.31, p = 0.64). Submandibular glands showed preferential involvement (Grade ≥ 1: left SMG 97.1% SLE, 85.7% RA). Power Doppler signals were more prevalent in SLE left SMG (77.1% vs 57.2%, p = 0.02), however this did not remain significant after correction for multiple comparisons. RA patients reported higher dryness scores (7.0 ± 1.83 vs 5.68 ± 1.92, p = 0.001) despite comparable structural findings. Anti-Ro/anti-La antibodies did not correlate with SGUS positivity in either group. SGUS showed no consistent correlation with disease activity measures and demonstrated moderate discriminative ability for ESSPRI-defined dryness ≥ 5 (AUC = 0.77, 95% CI 0.68-0.87).

Conclusion: SLE and RA patients exhibit comparable rates of salivary gland structural abnormalities independent of age, disease duration, and systemic inflammation. The discordance between ultrasonographic findings and patient-reported dryness, along with the lack of association with anti-Ro/anti-La antibodies, suggests heterogeneity in mechanisms of glandular involvement. SGUS provides objective assessment of glandular structure but should be interpreted alongside clinical evaluation and objective measures of gland function. Longitudinal studies incorporating objective salivary flow assessment are needed to clarify the clinical significance of ultrasonographic abnormalities.