Background: Sjogren´s syndrome (SS) is a chronic, systemic autoimmune disorder with a great clinical heterogeneity being an orphan disease at present ¹ . It is needed to find out new biomarkers to help us in the diagnosis, phenotype stratification and therapy of the disease. In a previous exploratory study we carried out in six serum and saliva samples from suspected SS patients we identified some proteins associated with SS ² .

Objectives: The aim of this study was to analyze sCD14 (soluble cluster of differentiation 14), CXCL10 (C-X-C Motif Chemokine Ligand 10), EGF (epidermal growth factor), PTX3 (pentraxine 3) and VEGFA (Vascular endothelial growth factor A) in serum samples and IL (interleukin)-6, IL-19 and ICAM1 (intercellular adhesion molecule-1) in saliva samples of suspected SS patients.

Methods: We included a cohort of 227 consecutive patients attended the rheumatology department for suspected SS: 60 patients met classification criteria from 2016 and/or 2002 (SS group), 79 patients had a labial minor salivary gland biopsy (MGSB) compatible with SS (MGSB ⁺ group) and 136 patients did not meet SS classification criteria nor had a compatible MGSB (control group).

Serum samples were collected and centrifuged at 1800g, divided into aliquots and stored at -80ºC. Saliva samples were cold collected to prevent degradation of proteins, centrifuged at 1800g at 4ºC and stored at -80ºC. We evaluated serum and saliva levels of the proteins using three different assays: Human CD14 Sandwich ELISA Kit (Proteintech) and two bead-based fluorescent multiplex kits, the Procarta Plex-4 plex (CXCL10, EGF, PTX3, VEGFA) (Invitrogen) and Human Luminex Discovery Assay (R&D system) in the case of ICAM1, IL-6 and IL-19. Statistical analysis were performed using the Mann–Whitney U test for independent samples with the SPSS v.18 software. P values ≤0.05 were defined as significant and values of 0.1< P > 0.05 were considered as borderline.

Results: We found increased levels of ICAM1 in the saliva samples of SS group patients: Median (Me):13,60 µg/ml, interquartile range (IQR): 3,59-45,979; P =0,011, compared to the control group (Me: 6,14 µg/ml, IQR: 2,15-14,22) and moreover we found increased levels of serum CXCL10 (Me: 5,78 pg/ml; IQR: 3,09-8,77; P =0,083) in SS group compared to the control group (Me: 5,03 µg/ml, IQR: 3,13-8,46), although only in this case of ICAM1 statistical significance was reached. When we analyzed the differences between MGSB ⁺ and control groups we found that patients from MGSB+ group showed significant increased levels of ICAM1(Me: 14,43 pg/ml; IQR: 5,55-48,08; P <0,001) and IL-6 (Me: 4,45 pg/ml; IQR: 1,59-12,01; P <0,032) in saliva as well as they had significant increased CXCL10 serum levels (Me: 6,30 pg/ml; IQR: 3,34-8,97; P <0,047) compared to control group (ICAM1: Me: 6,14 pg/ml; IQR: 2,15-14,22; IL-6: Me: 2,47 pg/ml; IQR: 1,19-5,31; CXCL10: Me 5,03 pg/ml; IQR: 3,13-8,46).

Conclusion: SS and MGSB+ groups of patients showed significant higher levels of ICAM1 in saliva compared to the control group. The analysis of this protein in saliva could be useful for the early diagnosis of SS patients.

REFERENCES: [1] Longhino S et al . Clin Exp Rheumatol 2023; 41: 2343-2356

[2] Santos-Bórnez, MJ. Ann Rheum Dis 2023, vol 82, suppl, 1: 1243,doi: 10.1136/annrheumdis-2023-eular.865

Acknowledgements: This study has been partially supported by the Sociedad de Reumatología de la Comunidad de Madrid (SORCOM). We would like to specially thank all the patients who have participated in this study.

Disclosure of Interests: None declared.