Salivary gland ultrasound in clinical practice: What is its real usefulness?

Salivary gland ultrasound (SGU) provides information about structural gland abnormalities that can be graded and used for primary Sjögren's syndrome (pSS) diagnosis. Its potential role as a prognostic marker for detecting patients at high risk of lymphoma and extra-glandular manifestations is still under evaluation. We aim to assess the usefulness of SGU for SS diagnosis in routine clinical practice and its relationship with extra-glandular involvement and lymphoma risk in pSS patients.

We designed a retrospective observational single-center study. Data was collected using the electronic health records of patients referred to an ultrasound outpatient clinic for evaluation over a 4-year period. Data extraction included demographics, comorbidities, clinical data, laboratory tests, SGU results, salivary gland (SG) biopsy, and scintigraphy results. Comparisons were made between patients with and without pathological SGU. The external criterion for comparison was the fulfillment of the 2016 ACR/EULAR pSS criteria.

A total of 179 SGU assessments were included from this 4-year period. Twenty-four cases (13.4%) were pathological. The most frequently diagnosed conditions prior to SGU-detected pathologies were pSS (9.7%), rheumatoid arthritis (RA) (13.1%), and systemic lupus (4.6%). One hundred and two patients (57%) had no previous diagnosis (sicca syndrome work-up); of these, 47 patients (46.1%) were ANA positive and 25 (24.5%) anti-SSA positive. In this study, the sensitivity and specificity of SGU for SS diagnosis were 48% and 98% respectively, with a positive predictive value of 95%. There were statistically significant relationships between a pathological SGU and the presence of recurrent parotitis (p=.0083), positive anti-SSB antibodies (p=.0083), and a positive sialography (p=.0351).

SGU shows high global specificity but low sensitivity for pSS diagnosis in routine care. Pathological SGU findings are associated with positive autoantibodies (ANA and anti-SSB) and recurrent parotitis.