Synovial alpha-defensin in native joints with inflammatory arthropathies

Objectives Synovial alpha-defensin has been established as a biomarker for periprosthetic joint infection (PJI). Little is known about the impact of non-infectious inflammation of native joints on synovial alpha-defensin. In rheumatoid arthritis (RA), elevated synovial alpha-defensin has been shown to be associated with erosive joint disease. This leads to the assumption that synovial alpha-defensin could be a general marker of inflammation also in other inflammatory arthropathies. Here we aimed to determine synovial alpha-defensin levels in symptomatic native joints of patients with any inflammatory arthropathy.

Methods In this retrospective analysis of n = 57 consecutive cases, we included all joint aspirations from patients that presented with an acute joint effusion of native joints for any reason but infection to our departments of rheumatology and orthopedics.

Replaced joints were excluded from the study. Synovial analysis included alpha-defensin ELISA, white blood cell (WBC) count, crystals and microbiology. In addition, serum C-reactive protein was determined. Operating with a cut-off value of 5.2 mg/L, alpha-defensin ELISA provided a semi-quantitative signal-to-cut-off ratio of 1.0.

Results and Conclusion The median alpha-defensin quotient in our cohort was 0.2 (95 % CI: 0.1 - 0.3; reference range: <1.0). Inflammatory arthropathies included RA (n = 27), spondyloarthritis (n = 9), gout (n = 6), psoriatic arthritis (n = 3), reactive arthritis (n = 3) and others (n = 9). There were no significant differences of synovial alpha-defensin levels between the different inflammatory arthropathies. Synovial alpha-defensin levels correlated significantly with WBC count (r = 0.66; p < 0.001) and serum C-reactive protein (r = 0.54; p< 0.001). Alpha-defensin quotients >1.0 were found in 22-33 % of all patients with an acute

non-infectious joint effusion.

Synovial alpha-defensin correlates with disease activity in different inflammatory arthropathies. It is elevated in up to one third of patients with an acute joint effusion secondary to exacerbated inflammatory arthropathies. Thus, a positive synovial alpha-defensin ELISA result (alpha-defensin quotient >1.0) is not suitable to diagnose bacterial joint infections in native joints with inflammatory arthropathy. Further studies are needed to investigate if different alpha-defensin cut-off values may be beneficial to discriminate between infectious and non-infectious joint effusions in inflammatory arthropathies.

Stichwörter a-defensin, alpha defensin, alpha-defensin, rheuma, joint infection

Publikationsverlauf

Artikel online veröffentlicht:
15. Oktober 2020