Salivary Gland Scintigraphy in Sjögren's Syndrome: A Retrospective Study of Diagnostic Accuracy and Correlation With Histological and Immunological Biomarkers.

Introduction Sicca syndrome, characterized by xerophthalmia and xerostomia, is associated with various autoimmune and non-autoimmune conditions, posing diagnostic challenges. Sjögren's syndrome (SS) is the most prevalent systemic autoimmune disease linked to sicca symptoms. This study evaluates the diagnostic accuracy of salivary gland scintigraphy (SGS) in distinguishing SS from non-Sjögren's sicca conditions, alongside other diagnostic tests. Methods A retrospective analysis was conducted at Hospital Universitario La Paz from December 2019 to March 2023, including 142 patients diagnosed with sicca syndrome. Correlations between qualitative and quantitative SGS data (GE Healthcare, Chicago, Illinois) and multiparametric sicca evaluations were assessed. Results Among the 142 patients, 84 (59.15%) were classified as having SS, with 55 (65.48%) seropositive for anti-Ro antibodies. Abnormal SGS results were found in 135 (95.07%) patients. Qualitative SGS categorized seven (4.93%) as mild, 53 (37.32%) as moderate, 50 (35.21%) as severe, and 21 (14.79%) as functionally annulled. Moderate or worse impairment had a sensitivity of 0.88 and a specificity of 0.17. Functional annulment had a sensitivity of 0.17 and a specificity of 0.97. Quantitative SGS using ejection fraction thresholds of ≤30% and ≤20% had sensitivities of 0.35 and 0.18 and specificities of 0.84 and 0.94, respectively. Quantitative SGS metrics correlated with unstimulated whole salivary flow (WUSF; 0.243; p=0.003) and inversely with lymphocytic infiltration (-0.281; p=0.001). The 2016 American College of Rheumatology/European League Against Rheumatism (ACR-EULAR) classification criteria for Sjögren's syndrome demonstrated an area under the curve (AUC) of 0.932, which improved to 0.951 with the inclusion of SGS parameters. Conclusions SGS is a significant diagnostic tool in the multiparametric evaluation of sicca syndrome, showing strong correlations with histological and immunological markers. Its integration into diagnostic criteria enhances the differentiation between SS and non-Sjögren's sicca conditions, suggesting its potential inclusion in future classification frameworks.