Synovial biopsy: an underutilized diagnostic tool in clinical practice: an observational study.

Background: Synovial biopsy, an important diagnostic tool to evaluate chronic monoarthritis, undifferentiated inflammatory arthritis and neoplasms, remains underutilized in clinical practice due to perceived invasiveness and limited access to specialized techniques. This study evaluates the diagnostic utility and histopathological spectrum of synovial biopsies in a tertiary care centre.

Materials and methods: This retrospective and prospective observational study was conducted over three years (June 2020-June 2023) in a tertiary care institute. Synovial biopsies obtained via needle biopsy or arthrotomy received in the Department of Pathology, were routinely processed and evaluated using Hematoxylin and Eosin (H&E) stain, with special stains wherever indicated.

Results: Total 148 synovial biopsies were analysed. The mean age was 49.9 years, M:F ratio was 1.7:1. The most common site was the knee joint (69.5%). Common histopathological diagnosis were chronic non-specific synovitis (46.6%), rheumatoid arthritis (RA) (16.2%), septic arthritis (12.8%), and tuberculous synovitis (11.5%). Diagnostic revision following histopathological examination occurred in 16 /148 cases (10.8%), significantly altering the clinical management. This included seven cases of tuberculosis (TB) initially presenting as acute synovitis, three cases of post-total knee replacement which were originally managed as bacterial infections but reclassified as TB following synovial biopsy and six cases of RA which were initially misclassified as osteoarthritis.

Conclusion: Synovial biopsy is a valuable investigation that can be incorporated into diagnostic algorithms for atypical presentations to improve patient outcomes and reduce clinical misclassification. In TB endemic regions, histopathological examination of synovial biopsy can prevent delayed diagnosis and suboptimal management.