The association of serum S100A8-A9 levels with disease activity, radiological findings and laboratory parameters in patients with psoriatic arthritis

S100A8 and S100A9 play a crucial role in immune system functions. S100 proteins are expressed in different cell types and have important roles in regulating various cellular processes and in the haemostasis of the immune system. The aim of this study was to investigate the association between serum S100A8/S100A9 levels and disease-related variables in patients with psoriatic arthritis (PsA), healthy controls, and individuals with psoriasis. 62 PsA patients, 52 healthy controls and 54 psoriasis patients were included. Sociodemographic and clinical characteristic of the groups were recorded. Serum levels of S100A8 and S100A9 were accessed in all groups by ELISA. In the psoriasis group, the S100A8 level was statistically lower and the S100A9 level was statistically higher than in the PsA and control groups. In the PsA group, there was a statistically significant positive correlation between S100A9 level and number of tender and swollen joints and DAPSA score. In the PsA group, there was a statistically significant negative correlation between S100A8 level and number of tender joints, VAS, DAPSA and BASDAI scores. In the PsA group, there was no significant correlation between S100A8-S100A9, CRP and ESR, MSHS and PASRI radiological scores. In psoriasis patients, we found positive correlation between BMI and S100A9 levels. S100A9 level, the number of swollen and tender joints in the PsA group correlated with DAPSA. S100A9 can be used as a new molecule in the follow-up of PsA disease activity, and it may be associated with psoriasis. The lower stability of S100A8 compared to S100A9 and its susceptibility to oxidation suggest that it may not be suitable for diagnosis of PsA. The results were showed that there are limitations regarding the use of these biomarkers in routine diagnosis and follow-up.