AB1253 Ultrasonographic signals have additive value for gout in patients presenting with mono-/oligoarthritis

Background Mono-/oligoarthritis (MOA) may be evoked by intra-articular crystals or other (rheumatic) disease. Crystal proof is an important diagnostic target for clinicians aiming at longterm prophylactic pharmacotherapy in gout. Barriers of this certainty in a diagnostic phase may be low availability of polarisation microscopy (PM) and/or joint puncture with diagnostic aspiration. We wondered whether ultrasonography (US) performs well enough to overcome these barriers in a diagnostic work-up to find crystal-associated diagnoses in our population presenting with MOA. Objectives To determine the additive diagnostic value i.e. positive predictive value of double contour sign for gout in patients presenting with a mono- or oligo-arthritis. Methods All patients presenting with MOA within a fixed period of time were seen by 2 rheumatologists performing US prior to needle puncture of the predominant arthritic joint and synovial fluid polarisation microscopy. Double contour sign (DCS), snowstorm and/or tophus supposedly specific for gout was searched for using US. In all patients 6 joints were visualized by US: knee (in flexion), MTP1 and wrist/ankle bilaterally. Results In a fixed period 34 patients, aged 34 to 73 yrs, with MOA were seen at our department: definitive diagnoses were gout 17 times (50%), and 17 X alternative (non-gout) arthritis. The most prominent arthritic joints were the wrist (6 times), knee (12 times), ankle (eight times), MTP1 (six times), and 2x other joints. Specific diagnostic features include a hyperechoic, irregular band over the superficial margin of the articular cartilage described as a DCS in 44% of all presented patients, and 73% of gouty patients, but also in 27% of the MOA without a crystal proven gout. Hypoechoic to hyperechoic, inhomogeneous material surrounded by a small anechoic rim, representing tophaceous material, was seen in a 4 patients and all crystal proven of the gouty patients. DCS’ sensitivity (positive predictive value (PPV) for gouty arthritis is 73%; prevalence of gouty arthritis: 17 out of 34 patients (50%) with a presenting MOA. In all these patient was gout crystal proven. In this mono/oligoarthritic Dutch patient population 50% suffers from gouty arthritis in whom crystal proof and 50% suffers from a non-crystal proven gout arthritis (cpp/reactive/psoriatic/rheumatoid arthritis), and Only 12% of the MOA and was tophaceous at presentation. N=34 patientsDCS +DCS – Gout MSU +11617 Gout MSU –41317 Total151934 Con