Background/Purpose: Current ultrasonographic scoring systems used to assess the degree of finger joint synovitis in rheumatoid arthritis (RA) are not designed for distinguishing healthy or osteoarthritis (OA) patients from those with RA in clinical settings. In this pilot study we explore a novel scoring approach using structural as well as quantitative synovial ultrasonographic features to distinguish between healthy and OA finger joints and those with RA.

Methods: 22 patients with RA, 16 healthy controls, and 14 OA controls received a comprehensive ultrasound of one hand’s metacarpophalangeal and proximal interphalangeal joints, with scores assigned using a modification of a previously reported  RA scoring system called the Semiquantitative Synovial Score (SSS), and using the novel approach called the Combined Structural/Synovial Score (CSSS). The SSS relied on the presence or absence of hypoechoic synovial tissue/fluid bulging over the lines between the joint-forming bones or extending to the diaphysis.  If either condition was met the joint was classified as supporting the diagnosis of RA (“RA-supported”). The CSSS utilized structural features of osteophyte and erosion, as well as measured thickness of the synovial cavity over the bony diaphysis and Doppler signal. If >1+ Doppler signal, >2mm of synovial thickness, or an erosion >1mm in two orthogonal planes was imaged the joint was classified as “RA-supported.”  The number of joints classified as “RA-supported” was tallied for each of the two scoring methods. Sensitivity and specificity for each method were calculated with respect to the clinical diagnosis of RA, and receiver operating characteristic (ROC) curves plotted across the range of possible scoring cutoffs.

Results: The SSS was highly sensitive (100%), but without specificity (0%) for the diagnosis of RA, when RA was defined as having more than 1 joint classified as “RA-supported.”  The CSSS had high sensitivity (95%) and moderate specificity (77%) when RA was defined as having any joint classified as “RA-supported”. Moderate sensitivity (73%) and high specificity (97%) were found when having more than 1 joint classified as “RA-supported” was required to diagnose RA.  Results of a sensitivity analysis of several different variations of the CSSS show some differences in the sensitivity and specificity of this system when different parameters are used such as volar or dorsal-only scans.

Conclusion: A novel combined structural and quantitative synovial hand joint scoring system was capable of distinguishing OA and healthy controls from RA subjects in this pilot evaluation.