The validity of salivary gland scintigraphy in Sjögren's syndrome diagnosis: comparison of visual and excretion fraction analyses.

Objectives: The diagnostic validity of salivary gland scintigraphy in Sjögren's syndrome (SS) has not been conclusively defined. Whether a quantitative (excretion fraction) interpretation of scintigraphy is superior to a qualitative one (visual analysis) remains a matter of debate. We sought to determine whether the diagnostic discrimination of excretion fraction is higher compared to that obtained by visual analysis.
Methods: Diagnostic test validity study that encompassed 137 suspected SS subjects who underwent scintigraphy for diagnostic purposes. Patients were diagnosed as SS and non-SS according to the rheumatologist's clinical judgment, and by using the American-European Consensus Group (AECG) and American College of Rheumatology (ACR) classification criteria. Visual analysis (normal vs. abnormal and Schall's classification grade) and excretion fraction scores were calculated. The diagnostic discrimination of these methods was compared through the area under the curve (AUC) analysis. Scintigraphy associations with SS clinical and laboratory features were assessed through multivariable regression analysis.
Results: Schall's classification AUC reached statistical significance in its diagnostic discrimination for SS clinical judgment (0.704 [95%CI 0.597-0.811]) and AECG criteria (0.764 [95%CI 0.641-0.886]). Similarly, submandibular excretion fraction was associated with SS diagnosis based on ACR (0.737 [95%CI 0.546-0.931]) and AECG criteria (0.715 [95%CI 0.597-0.833]). However, AUC comparisons between qualitative and quantitative methods did not yield statistically significant values. Both interpretation modalities were associated with SS serological features. Moreover, excretion fraction was also associated with salivary gland biopsy.
Conclusions: SS diagnostic discrimination of excretion fraction is not superior to that obtained by qualitative visual analysis. Both qualitative and quantitative scintigraphy methods are associated with SS clinical and laboratory characteristics.