Background Salivary gland assessment is important for diagnosing primary Sjögren’s syndrome (pSS), as the lymphocytic focus score (LFS) is part of pSS classification criteria. Quantitative immunohistology (QIH) is another technique used for assessing pSS in which the percentage of immunoglobulin-specific plasma cells is measured, with IgA <70% and/or IgM >10% as positive criteria.
Objectives To investigate the prognostic value of minor salivary gland assessment (LFS and QIH) for disease severity of pSS.
Methods Medical charts of 174 pSS patients were retrospectively analyzed, comparing histology results (LFS and percentages of IgA, IgM and IgG plasma cells) with disease outcomes as non-Hodgkin lymphoma (NHL) and clinical scores: cumulative EULAR Sjögren’s Syndrome disease activity index (ESSDAI) and the number of extraglandular manifestations (EGM) during disease course.
Results Mean age at pSS diagnosis was 47±14 years and median follow-up after biopsy was 105 months (range 10–408). LFS ≥1 were seen in 99%, <70% IgA-positive plasma cells in 90%, and >10% IgM-positive plasma cells in 71% of patients. The number of foci correlated to a decrease in the percentage of IgA-positive plasma cells (R=0.315, p=0.0001). NHL developed in 16 patients (9%). The mean LFS was significantly higher in patients with NHL (3.0±0.9 versus 2.3±1.1; p=0.021). The threshold of ≥3 foci had a positive predictive value of 16% for development of lymphoma, and a negative predictive value of 98% (OR 7.9; p=0,008). QIH results could not predict lymphoma development. Only LFS ≥3 contributed significantly and independently to NHL development in a hierarchical multiple regression model, correcting for presence of anti-SSA/SSB antibodies (beta 0.244; p=0.017). Cumulative ESSDAI and EGM were significantly correlated to LFS, a decreased percentage of IgA-positive and an increased percentage of IgM-positive plasma cells (R range 0.166–0.284; p≤0.04), but not to the percentage of IgG-positive plasma cells.
Conclusions Routinely performed minor salivary gland assessments have important prognostic value. The number of lymphocyte foci can be used to identify patients with increased lymphoma risk.
Acknowledgements We would like to thank J.M van Woerkom, R. Goldsmeding and the pathology department of the University Medical Center Utrecht for their work on the minor salivary gland assessments.
Disclosure of Interest None Declared
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