Objective: To develop an ultrasonographic (US) synovitis scoring system suitable for evaluation of finger joint inflammation in patients with active rheumatoid arthritis (RA) and to compare semiquantitative US scoring with quantitative US measurements.
Methods: US was performed at the palmar and dorsal sides of the second through fifth metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints in 10 healthy subjects and in the clinically more affected hand in 46 RA patients. Ten patients additionally underwent magnetic resonance imaging (MRI). Synovitis was measured, standardized, and scored according to a semiquantitative method. The 2 methods (semiquantitative US scoring, quantitative US) were compared and statistical cutoffs were identified using receiver operating characteristic (ROC) curve analysis. MRI results were compared with semiquantitative US scoring and quantitative US results. The optimal US scoring method from 6 joint combinations was identified (ROC curve analysis).
Results: Synovitis was most frequently detected in the palmar proximal area (86% of affected joints). We found no significant differences between individual PIP joints or between individual MCP joints, indicating that all fingers within each of these joint groups should be treated equally for statistical calculations, although each joint group as a whole should be treated separately. The optimal cutoff point to distinguish between "health" and "pathology" was 0.6 mm both for MCP joints (sensitivity 94%, specificity 89%) and for PIP joints (sensitivity 90%, specificity 88%). There was no significant difference between semiquantitative US scores and quantitative US measurements. The best results for joint combinations were achieved using the "sum of 4 fingers" (second through fifth MCP and PIP joints) and "sum of 3 fingers" (second through fourth MCP and PIP joints) methods. Comparison of MRI results with semiquantitative US scores revealed high concordance.
Conclusion: US evaluation of finger joint synovitis can be considerably simplified by focusing on the palmar side and by applying semiquantitative grading instead of quantitative measurements. For evaluation of treatment efficacy based on synovitis in RA patients, we recommend using the "sum of 3 fingers" method in longitudinal trials.