Ultrasonographic Evaluation of Salivary Gland Stiffness in Primary Sjögren's Disease and Idiopathic Xerostomia

BACKGROUND: Ultrasonography is widely used to evaluate salivary gland involvement in primary Sjögren's disease (SjD). However, distinguishing SjD-related dry mouth from idiopathic xerostomia (IX) remains challenging. This study evaluates whether elastography, an advanced ultrasonographic technique measuring gland stiffness, can improve differentiation. METHODS: In this retrospective study, 192 patients diagnosed with SjD (n = 83) or IX (n = 109) were assessed for xerostomia severity and underwent conventional, Doppler ultrasonography, and shear wave elastography (SWE) of salivary glands. Additional SjD-related indicators, including serological and pathological markers, were analyzed. Univariate and multivariate logistic regression identified key differentiators, and generalized additive model (GAM) examined nonlinear associations. RESULTS: SjD patients showed significantly higher parotid gland stiffness (23.9 ± 10.9 kPa) compared to IX patients (15.1 ± 6.7 kPa, p < 0.0001). Additionally, submandibular gland homogeneity and parotid stiffness were independent predictors of SjD. Multivariate analysis revealed parotid stiffness as the strongest factor associated with SjD (OR = 1.152 per kPa increase, 95% CI: 1.080-1.241). GAM analysis revealed a nonlinear exposure-response pattern, with the modeled proportion of SjD reaching approximately 50% at a parotid stiffness of 17.7 kPa. CONCLUSION: Parotid gland stiffness shows promise as a clinical tool for distinguishing SjD from IX.