MA: ultrasound is reasonably accurate in detecting synovitis in patients with rheumatoid arthritis

Reference

Takase-Minegishi K, Horita N, Kobayashi K, et al. Diagnostic test accuracy of ultrasound for synovitis in rheumatoid arthritis: systematic review and meta-analysis. Rheumatology (Oxford) 2018;57(1):49-58.

Synopsis

The presence of synovitis in patients with rheumatoid arthritis is associated with developing joint destruction, and early intervention improves outcomes. So, these authors systematically searched several databases for studies that evaluated the accuracy of ultrasound compared with MRI for the detection of synovitis in patients with rheumatoid arthritis. Although MRI is a convenient tool, and has become the noninvasive reference standard for many conditions, it is arguably less reliable than tissue-based diagnostic standards. Two authors independently assessed each study for inclusion, then assessed the quality of the included studies and had a "discussion" in the event of disagreements. The authors also graded the quality of the MRIs on the basis of the power of magnet, use of contrast, resolution, and so forth (reinforcing the idea that MRI is a problematic gold standard). Although this study was not funded, 2 of the authors have significant relationships with industry. Ultimately they included 14 studies: 5 studies assessed a total of 275 wrists, 12 stuides assessed more than 2060 metacarpophalangeal joints (MCP), 6 studies assessed 1073 proximal interphalangeal joints (PIP), and 2 studies evaluated 31 knees. Compared with MRI the overall accuracy for ultrasound was slightly better for finger joints than for wrists (area under the receiver operator characteristic curve = 0.91 for fingers, 0.81 for wrists) and not very accurate for knees (0.61). When the result was abnormal the ultrasound was pretty reliable, but when the result was normal the ultrasound was only modestly reliable. The positive and negative likelihood ratios (LR+ and LR-, respectively) and 95% confidence intervals for each joint are as follows: Wrist: LR+ 3.3 (0.9 - 14.5), LR- 0.3 (0.1 - 1.1) MCP: LR+ 9.1 (3.6 - 27), LR- 0.3 (0.2 - 0.6) PIP: LR+ 11.8 (1.6 - 31), LR- 0.3 (0.07 - 0.8) Knee: LR+ 2.3 (0.7 - 10), LR- 0.2 (0.01 - 2.2) Just a reminder: A likelihood ratio of 1 provides no useful information; values less than 0.1 or greater than 10 provide the most useful information. The confidence intervals in these studies are wide enough to dampen the authors' conclusions that ultrasound is accurate enough in detecting synovitis in the fingers.