Head-to-head comparison of ultrasound and 99m Tc-glucosamine SPECT/CT imaging of patients with rheumatoid arthritis: a single center prospective study

Background Rheumatoid arthritis (RA) is an inflammatory disease that can lead to progressive joint damage. Early identification of synovitis is key in the management of patients with RA. The aim of this study was to assess synovitis in patients with RA using 99m Tc-glucosamine single photon emission computed tomography/computed tomography (SPECT/CT) imaging and compare this radiopharmaceutical's diagnostic performance with ultrasound (US) imaging. This prospective study included 22 participants with active RA and 380 joints were assessed with SPECT/CT and US imaging. SPECT/CT imaging of the joints of interest was performed in each participant three hours after injection of 99m Tc-glucosamine, with US imaging of the same joints performed on the same day. The affected joints were qualitatively assessed for 99m Tc-glucosamine uptake and compared with the findings on US imaging. Results Abnormal increased uptake of 99m Tc-glucosamine, localized specifically to the synovial space, was noted in the affected joints. The overall sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and diagnostic accuracy of 99m Tc-glucosamine SPECT/CT imaging were 86%, 60%, 61%, 85% and 73%, respectively. A sensitivity of 100% was noted in the identification of synovitis in the carpal and knee joints. Disease activity in the distal interphalangeal (DIP) joints was not observed with either SPECT/CT or US. Conclusions SPECT/CT imaging with 99m Tc-glucosamine is a valuable tool for assessing disease activity in the joints of patients with RA. It has a very high sensitivity in detecting synovitis and it correlates very well with US imaging in this regard.