Synovial fluid and serum concentretions of inflammatory markers in rheumatoid arthritis, psoriatic arthritis and osteoarthritis: a systematic review

Background: The aim of this review is to investigate systematically the presence of the most extensively studied synovial fluid (SF) and/or serum markers in patients with rheumatoid arthritis (RA), psoriatic arthritis (PsA) and osteoarthritis (OA), and their associations and correlations with laboratory and clinical data, with a view to providing insights for future research. Objective: Papers were selected using the PRISMA flow-chart. Search of the electronic databases according to the above criteria found a total of 55 papers. Examination led to the exclusion of 39 papers. Finally, 16 studies met the inclusion criteria and are reviewed. As regards to interleukins we found: higher TNF-α levels in patients with early RA and PsA than in those with osteoarthritis (p<0.05); higher IL-6 levels in patients with inflammatory arthritis (RA and PsA) than in those with OA (p=0.032) and higher IL-17 levels in SF from PsA patients than RA patients (p=0.04) and a sig- nificant difference in serum levels between PsA patients and healthy controls (p=0.013) and higher IL-22 SF levels in PsA than OA patients (p<0.001) and in RA compared with OA patients (p<0.01). As regards chemokine, CCL-22 was higher in SF from RA and PsA patients than in OA patients (p<0.01). Method: Considering the sample size of the studies reviewed here, their findings need confirmation in larger samples, while the potential prognostic value of SF and/or serum biomarkers requires prospective investigation. Conclusion: The limitations of the biological SF assays and the problems encountered in the attempted use of cytokine assays for diagnostic purposes must be addressed.