Association of salivary inflammatory biomarkers with primary Sjögren's syndrome

Background Primary Sjogren's syndrome (pSS) is an autoimmune disease that leads to salivary and lacrimal gland dysfunction. The adaptive immune response associated with T helper‐2 lymphocytes appears to be altered in these patients. Therefore, the objective of this study was to determine the salivary levels of interleukin (IL)‐6, IL‐5, and IL‐4 in patients with pSS when compared to a healthy control (HC) group. The secondary objectives were to study whether ILs levels in pSS patients were associated with salivary flow, patient‐reported outcomes (PROMs) for xerostomia and oral health quality of life (Oral Health Impact Profile‐14 [OHIP‐14]), pSS classification criteria and presence of extraglandular manifestations. Methods A case‐control study was conducted in 36 patients with pSS and 35 HCs. Cytokine levels were measured using high‐sensitivity multiplex map human immunoassays. Unstimulated and stimulated whole saliva were collected and patients filled out questionnaires. The Mann‐Whitney U test, chi‐squared test, and Spearman correlation test were used. Results Interleukin‐6 was significantly higher in pSS patients than in HCs (P = .0001). IL‐6 was significantly higher in pSS patients with a positive salivary gland biopsy (P = .04), whole stimulated saliva hyposalivation (P = .02), and presence of musculoskeletal disorders (P = .03). There was a non‐significant positive correlation between IL‐6 levels and PROMs for xerostomia (r = .31; P = .06) and OHIP‐14 (r = .07; P = .68) in pSS patients. Levels of IL‐4 and IL‐5 were not detected in both pSS and HCs patients. Conclusions Salivary IL‐6 levels are significantly associated with pSS patients, and therefore, it is hypothesized that this biomarker may be useful in the diagnosis and follow‐up of this disease.