Ultrasound-guided synovial biopsy improves diagnosis of septic arthritis in acute arthritis without enough analyzable synovial fluid: a retrospective analysis of 176 arthritis from a French rheumatology department.

To assess the diagnostic value of ultrasound-guided (US-guided) synovial biopsy in routine clinical practice in cases of acute and chronic arthritis. A retrospective, single-center study of US-guided synovial biopsies between 2003 and 2013. The clinical, laboratory, radiographic, synovial fluid, and histological and bacteriological results of synovial biopsies were analyzed. Arthritis was classified according to disease duration < 6 weeks (AA) or ≥ 6 weeks (CA). Synovial biopsy success rate was defined by the rate of capsular and/or synovial tissue analyzed. The diagnostic efficiency was defined by synovial biopsy success rate multiplied by the clinical utility (validation of a diagnostic hypothesis leading to a specific therapy). One hundred seventy-six US-guided synovial biopsies (51 AA and 125 CA) were analyzed. Synovial biopsy success rate was 82.4%. The diagnostic efficiency was 19.9%. Among the acute arthritis cases, 11 were septic. Only three patients had a positive biopsy culture while the synovial fluid puncture was of insufficient quantity to allow bacteriological analysis. The perivascular infiltration of neutrophils (PMN) had a sensitivity of 81.8%, a specificity of 84.2%, and a positive likelihood ratio of 5.2 for the septic arthritis diagnosis. Among the chronic arthritis cases, no case of pyogenic septic arthritis was found. No histological lesions, examined separately, were specific to a type of chronic inflammatory joint disease. US-guided synovial biopsies remain relevant for the diagnosis of septic arthritis, in cases of acute arthritis when joint aspiration is not possible.