Abstract / Summary
Background: Monoarticular ankle arthritis has a broad differential diagnosis, and establishing the underlying aetiology can be challenging when initial clinical, laboratory, and imaging investigations are inconclusive.Ultrasound-guided synovial biopsy enables tissue sampling for histopathological and microbiological evaluation.This study evaluated the histopathological findings and potential role of ultrasound-guided synovial biopsy in patients with undifferentiated monoarticular ankle arthritis.Methods: This prospective, single-centre exploratory study was conducted at Bangladesh Medical University, Dhaka, Bangladesh, from January to December 2025.Thirty consecutive adults with monoarticular ankle arthritis underwent standardised clinical, laboratory, and imaging evaluation.Eight patients (26.7%) received a clinical diagnosis without biopsy, whereas 22 (73.3%) with undifferentiated arthritis underwent ultrasound-guided synovial biopsy.Within the biopsy cohort, a prespecified histopathological classification was used to classify cases as tuberculous or nontuberculous arthritis; this classification was not considered an independent microbiological reference standard.The GeneXpert Mycobacterium tuberculosis/rifampicin (MTB/RIF) assay (Cepheid, Sunnyvale, CA, USA) and acid-fast bacilli (AFB) staining were performed on available synovial tissue and fluid specimens.Sensitivity, specificity, and diagnostic accuracy were calculated with exact 95% CIs.Results: Among the 30 participants, 22 (73.3%) had undifferentiated arthritis and underwent biopsy.Their mean age was 38.5 ± 15.0 years, and 17 of the 22 (77.3%) were male.Based on the prespecified histopathological classification, five of the 22 (22.7%) were classified as having tuberculous arthritis and 17 (77.3%)as having nontuberculous arthritis, most commonly nonspecific synovitis.Granulomatous inflammation was present in all five (100.0%)classified tuberculous cases and zero of the 17 (0%) nontuberculous cases (p < 0.001).Epithelioid cell granulomas and caseous necrosis were present in four of the five (80.0%) and three of the five (60.0%) classified tuberculous cases, respectively.Tissue GeneXpert MTB/RIF showed a sensitivity of 60.0% (3/5; 95% CI, 14.7-94.7%),specificity of 100.0%(17/17; 95% CI, 80.5-100.0%),and diagnostic accuracy of 90.9% (20/22).Synovial-fluid GeneXpert MTB/RIF showed a sensitivity of 20.0% (1/5; 95% CI, 0.5-71.6%),specificity of 100.0%(17/17; 95% CI, 80.5-100.0%),and diagnostic accuracy of 81.8% (18/22).AFB staining of tissue and synovial fluid each showed a sensitivity of 20.0% (1/5; 95% CI, 0.5-71.6%),specificity of 100.0%(17/17; 95% CI, 80.5-100.0%),and diagnostic accuracy of 81.8% (18/22).Conclusions: Ultrasound-guided synovial biopsy may provide useful diagnostic information in selected patients with undifferentiated monoarticular ankle arthritis, particularly when tuberculosis is suspected.Histopathological examination and molecular testing of synovial tissue may complement clinical, radiological, and microbiological assessment.However, these findings should be interpreted cautiously because of the exploratory study design, small number of tuberculous cases, and absence of an independent microbiological reference standard.Larger prospective studies incorporating mycobacterial culture, molecular testing, histopathology, and longitudinal follow-up are warranted to further define the role of ultrasound-guided synovial biopsy.