Background:Sjögren’s syndrome (SS) is a chronic inflammatory autoimmune disease characterized by lymphocyte infiltration in salivary and lacrimal glands. Recently, salivary gland ultrasonography (US) proved valuable for assessing salivary gland involvement in SS and seemed to exhibit good diagnostic properties. In the literature, studies conducted by the scoring of the structural changes according to B-Mode US of salivary glands showed a wide variability regarding sensitivity and specificity. Our previously study demonstrated that although conventional B-mode US findings were useful for the diagnosis of SS with low salivary flow they were not for subclinical SS with normal salivary flow (EULAR 2016). Recently, we reported that the tissue elasticity was decreased due to structural changes in the submandibular glands (SG) at the advanced stage of the disease and the shear wave elastography (SWE) is useful to distinguish pathological changes of the SG in patients with SS (EULAR2018).Objectives:The aim of this study was to compare the usefulness of SG conventional B-mode US and SWE findings in non-SS and SS patients classified by salivary flow.Methods:Twenty-two non-SS patients and 99 SS patients who fulfilled the American College of Rheumatology (ACR) / European League Against Rheumatism (EULAR) classification criteria for SS were studied. SS patients were divided into three groups according to salivary flow using gum test (VL/SS <5mL/10min. (n=38), L/SS 5-10mL/10min. (n=41) and N/SS >10mL/10min. (n=20)). All patients were examined SGUS by a single investigator who was blinded to device (TUS-A300; Canon Medical Systems, Tokyo, Japan) with a linear transducer (7.5-10MHz). The examination consisted of conventional B-mode US (US staging score), pulsed wave Doppler US (PD grading score) and SWE with quantitative assessment. US staging scores were assessed by glandular size, inhomogeneity and contrast of diagastric muscle (stage 0 to 3). PD grading scores were graded by pulsed wave pattern in pulsed wave Doppler US at the internal SG facial arteries (grade 0 to 2). With the region-of-interest (ROI) placed over the stiffest areas of the lesion on SWE, the quantitative means of the elasticity values were measured by shear wave velocity (Vs; m/s) and elasticity (E; kPa) for each lesion.Results:The US staging score, the PD grading score, the values of Vs and E were significantly higher in patients with SS than in non-SS group (SS vs non-SS; US staging score 2.10±1.07 vs 0.86±0.99, p<0.0001, PD grading score 1.17±0.83 vs 0.23±0.61, p<0.0001, Vs 1.75±0.34 vs 1.57±0.29m/s, p=0.02, E 9.64±4.02 vs 7.81±2.27kPa, p=0.04). However, there was no significant difference between non-SS and N/SS in early-stage SS by US staging score (N/SS vs non-SS; 0.95±0.89 vs 0.86±0.99) and PD grading score (N/SS vs non-SS; 0.40±0.15 vs 0.23±.061). In contrast, the values of Vs and E were highest in N/SS as compared with all groups, and were significantly higher in N/SS than in non-SS (N/SS vs non-SS; Vs 2.02±0.24 vs 1.57±0.29m/s, p<0.01, E 12.58±3.16 vs 7.81±2.27kPa, p<0.01).Conclusion:The present study demonstrated that although the tissue elasticity was decreased due to structural changes at the advanced stage, it increased due to inflammation and high viscosity in the SG at the subclinical SS with normal salivary flow comparing that in non-SS patients. The SWE may be a useful tool for the differential diagnosis between patients with non-SS and subclinical SS with normal salivary flow, which is difficult to distinguish by conventional B-mode US.Disclosure of Interests:None declared
How to perform shear wave elastography. Part I