TY - JOUR T1 - Is the Double Contour Sign Specific for Gout? Or Only for Crystal Arthritis? JF - The Journal of Rheumatology JO - J Rheumatol SP - 353 LP - 354 DO - 10.3899/jrheum.141322 VL - 42 IS - 3 AU - JASVINDER A. SINGH AU - NICOLA DALBETH Y1 - 2015/03/01 UR - http://www.jrheum.org/content/42/3/353.abstract N2 - In this issue of The Journal, Löffler, et al describes a study assessing the sonographic double contour (DC) sign in gout, calcium pyrophosphate crystal deposition (CPPD), and other arthritides1. They investigated the diagnostic value of the DC sign alone and in combination with Doppler signals and serum uric acid (SUA) levels in patients presenting with acute arthritis by examining 225 acutely inflamed joints. Cartilage enhancements presenting as a parallel line to the bony articular surface were defined as the DC sign. All patients underwent synovial fluid analysis that was used to make the diagnosis of gout or CPPD or other arthritides, independent of the joint ultrasound (US) findings. The sensitivity of the DC sign for crystal arthritis was 85% and specificity was 80%. Its specificity for gout was 64%, and for CPPD 52%. The combination of DC sign with hypervascularization in Doppler studies and elevated SUA levels increased specificity for gout to 90% and resulted in a 7-fold increase of likelihood of gout (p < 0.01), albeit at the expense of sensitivity (42%). The study has several strengths, including use of a large patient sample, confirmation of diagnosis by crystal examination, and appropriate acute arthritis controls. The study findings must be interpreted considering potential limitations and these findings need to be compared and contrasted with those from other studies of US in gout.A striking finding of this study reporting the use of US in real-world clinical practice was the inability of the DC sign to differentiate between gout and CPPD. In previous US publications, the differential cartilage … Address correspondence to Dr. J.A. Singh, University of Alabama, Faculty Office Tower 805B, 510 20th St. S, Birmingham, Alabama 35294, USA. ER -