124. Ultrasound-Guided Diagnostic Synovial Biopsies: An Audit of a Rheumatology-Led Service

Abstract

Background: Diagnostic synovial biopsies (Bx) are key investigations which traditionally involves an invasive orthopaedic arthroscopic procedure. Within our rheumatology department, we currently use a minimally invasive ultrasound (US) guided synovial biopsy technique for both research and diagnostic synovial tissue sampling. This audit was undertaken to review our diagnostic Bx activity and outcome with respect to quality of tissue obtained and procedure safety. Methods: 26 patients underwent an outpatient diagnostic synovial biopsy from May 2011 to October 2012. Data were collected from case notes and online care record system. Bx were performed in sterile aseptic conditions in a procedure room. After local anaesthesia, a 16G core Bx needle is placed within the joint capsule under US visualization and is guided to the appropriate site for sampling. Tissue samples were placed in formalin for histology analysis, but kept fresh for microbiology and crystal analysis. Results: Activity: Joints Biopsied-knees (n=8, 31%), wrists (n=6, 23%) flexor tendon sheaths (n=2, 8%), MCPJs (n=2, 8%), MTPJs (n=2, 8%), ankles (n=2, 8%), shoulder, elbow, PIPJ and DIPJ(n=1 each, 4%). The commonest indication was to exclude septic arthritis (n=18, 70%), followed by requests for confirmation of a crystal arthritis (n=4, 15%) and sarcoidosis (n=4, 15%). Timing of Bx: 78% of all Bx were performed within 5 days of request, 54% within 3 days and 31% within 1 day. Tissue quality: All samples harvested were of good quality for laboratory processing bar 1 biopsy with insufficient tissue for histopathology but sufficient for microbiology analysis. Safety: A majority of patients (92%) had an uncomplicated Bx. 2 patients (8%) described arthralgia and swelling at Bx site 48 hours post procedure. No evidence of haemarthrosis or infection was found and pain settled with simple analgesia after 2 days. Outcome: 4 cases of TB arthritis were diagnosed (22%, 4/18). 2 patients had granulomas seen on histology, 2 other patients had positive mycobacteria on MC&S. For those suspected sarcoid cases, one Bx of the flexor tendon sheath had granulomas on histology with negative IGRA suggesting sarcoid tenosynovitis. No crystals were seen in any of the samples harvested for cases suspected of crystal arthritis. Patients with negative Bx results went on to be diagnosed with undifferentiated inflammatory arthritis and were treated with disease modifying drugs. To date, none of these patients were subsequently treated for an infected arthritis (mean follow-up 26 months). Conclusion: A minimally invasive US guided synovial biopsy performed by rheumatologists is well tolerated and has utility in providing quick tissue sampling for microbiology and histology analysis. Further studies should be considered to determine the negative predictive value of this tool in the context of suspected septic arthritis.