GÖTTINGEN, Germany  – The first prospective, long-term comparison of ultrasound (US), magnetic resonance imaging (MRI), and conventional radiography (CR) finds that US and MRI are better methods for monitoring clinical improvement and regression of synovitis in rheumatoid arthritis (RA) finger joints during long-term treatment with disease-modifying anti-rheumatic drugs (DMARDs) and recommends US as the most cost-effective tool for routine follow-up. The 7-year follow-up data1 are reported in Annals of the Rheumatic Diseases by Alexander K. Scheel, MD, of the Georg-August-Universität Göttingen in Göttingen, Germany. The main objective of this study was to collect longitudinal data on the accuracy of US, MRI, and CR for detecting synovitis and bone erosions in the finger joints of patients with RA who were being treated with DMARDs. The researchers also set out to determine whether radiographically occult finger joint erosions identified at baseline by US and MRI would appear on CR at the 7-year follow-up point.

"Both imaging techniques are good for diagnosis and follow-up analysis; however, since US is less cost intensive and as precise, it is a good alternative for follow-up analysis." — Alexander K. Scheel, MD
The investigators found that all three imaging techniques detected an increase of bone erosions over the 7-year period, but only US and MRI detected clinical improvement and regression of synovitis. More than one-third of erosions previously detected by MRI were seen by CR seven years later, suggesting either the healing of some erosions in DMARD-treated patients, reader error, or technical limitations of the conventional x-ray procedure, the authors write.

Findings may change clinical practice

"MRI and US are new imaging techniques that are sensitive in the detection of soft tissue changes in RA finger joints, which equal early arthritis findings, but are also able to detect erosions earlier than radiography," Dr. Scheel told CIAOMed. "Both imaging techniques are good for diagnosis and follow-up analysis; however, since US is less cost-intensive and as precise, it is a good alternative for follow up analysis," he said, pointing out that MRI is too expensive to be the imaging gold standard.

Dr. Scheel told CIAOMed that he hopes the findings will change clinical practice, and indicated that clinicians should "use more US for detection and follow-up of inflammation in RA finger joints. An early diagnosis is important for early and aggressive treatment," he said, noting that  "American College of Rheumatology (ACR) criteria do not catch early arthritis patients, and there is a lack in the detection of synovitis with radiography, underlining the importance of new imaging techniques."

In the prospective, 7-year follow-up imaging study, researchers compared CR, US, and MRI in the detection of bone erosions and synovitis in RA finger joints. The analysis included the metacarpophalangeal and proximal interphalangeal joints II-V (128 joints) of the clinically dominant hand of 16 patients with RA . The researchers also made joint by joint follow-up comparisons for erosions and synovitis.

At baseline, CR detected erosions in 5/128 (4%) of all joints, US detected erosions in 12/128 (9%), and MRI detected erosions in 34/128 (27%), the study showed. Seven years later, an increase of joints with erosions was found with CR (26%), US (49%) (P <.001 each), and MRI (32%, NS). By contrast, joint swelling and tenderness assessed by clinical examination were decreased at follow-up (P = .2, P <.001). A significant reduction in synovitis was seen with US and MRI (P <.001 each); in CR, 12 patients did not have any erosions at baseline, while in 10/12 patients erosions were detected in 25/96 (26%) joints after 7 years. US initially detected erosions in 9 joints, of which two of these joints with erosions were seen by CR at follow-up. MRI initially found 34 erosions, of which 14 (41%) were then detected by CR, the study found.

US versus MRI

During long-term DMARD treatment, there was a significant reduction in synovitis with both US and MRI, but the reduction was more evident with US. In fact, US was sensitive for the detection of very small fluid accumulations and proved better than MRI, especially in the proximal interphalangeal (PIP) joints, Dr. Scheel and colleagues report.

MRI seems to be better than US for detecting early erosions because more of the erosions formerly detected by MRI were seen by CR at follow-up, the study showed. However, Dr. Scheel points out that this might be partly explained by the less sensitive US equipment available at the time of the baseline measurements.

The investigators conclude, "Both techniques have their advantages and disadvantages.... However, because US is an easy-handling and low-cost imaging technique, whereas MRI is rather expensive, we recommend US for quick evaluation of follow-up analysis."

Reference

  1. Scheel AK, Hermann K-G A, Ohrndorf S, et al. Prospective 7-year follow-up imaging study comparing radiography, ultrasonography, and magnetic resonance imaging in rheumatoid arthritis finger joints. Ann Rheum Dis. 2006;65:595-600.