Normal-Appearing Salivary Gland Ultrasonography Identifies a Milder Phenotype of Primary Sjögren's Syndrome

Objective: Salivary gland ultrasound (SGUS) is emerging as a valid tool in the management of primary Sjogren's syndrome (pSS). This study aimed to investigate whether pSS patients with normal-appearing or pathological SGUS findings showed different clinical, laboratory, and pathologic pSS-related features, and to compare the results by using two different SGUS scores.Methods: Consecutive pSS patients, according to the ACR-EULAR classification criteria, were evaluated. Salivary glands were scored using the early 1992 score by De Vita et al. and the latest 2019 OMERACT score, both being semiquantitative 0-3 scoring systems focused on ultrasonographic parenchymal inhomogeneity (grades 0 and 1, normal-appearing; grades 2 and 3, pathological). The patients were then divided into two groups: "SGUS normal-appearing" if all the salivary glands had normal-appearing parenchyma (grade 0 or 1), or "SGUS pathological" if the grade was 2 or 3 in at least one salivary gland. The associations between SGUS and pSS-related clinical, laboratory, and pathological features were then investigated in the two groups.Results: One hundred pSS patients were evaluated, the mean age (+/- SD) was 60.9 +/- 12.0 years, and mean disease duration was 11.7 +/- 7.2 years. Twenty-nine out of 100 (29%) patients were in the "SGUS normal-appearing" group and 71/100 (71%) were in the "SGUS pathological" group. A normal-appearing SGUS was significantly associated with the absence of anti-La/SSB antibodies (p < 0.001) and normal unstimulated salivary flow rate (p = 0.02) by both univariate and multivariate analyses. By univariate analysis, a normal-appearing SGUS was significantly associated also with the absence of rheumatoid factor (p = 0.002) and of serum monoclonal component (p = 0.003), ESSDAI < 5 (p = 0.03), and with a negative lip biopsy (p = 0.029). No associations were found with other items, including anti-Ro/SSA (p = 0.145), Schirmer's test (p = 0.793), ESSPRI (p = 0.47), and demographic data. No differences in these results were observed by using the two SGUS scoring systems.Conclusion: The SGUS allowed the identification of different phenotypes of pSS, and different SGUS scores focused on salivary gland inhomogeneity may be effective to this end.