RESEARCH - Bone marrow edema is the most specific finding for RA on noncontrast MRI

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J Rheumatol. 2009 Dec 1.

Bone Marrow Edema Is the Most Specific Finding for Rheumatoid

Arthritis (RA) on Noncontrast Magnetic Resonance Imaging of the Hands

and Wrists: A Comparison of Patients with RA and Healthy Controls.

Olech E, Crues JV 3rd, Yocum DE, Merrill JT.

From the Oklahoma Medical Research Foundation, Oklahoma City,

Oklahoma, USA; Radnet Management, Los Angeles, California, USA; and

Stanford University, Palo Alto, California, USA.

OBJECTIVE: To evaluate the sensitivity and specificity of magnetic

resonance imaging (MRI) in detecting erosions, bone edema, and

synovitis in the metacarpophalangeal and wrist joints for rheumatoid

arthritis (RA).

METHODS: MRI scans of bilateral hands and wrists of 40 healthy

subjects and 40 RA patients were performed using 0.2 T extremity-MRI

and read blindly using a modified RA MRI (RAMRIS) system (no contrast

injection, imaging in 1 plane only). To determine interreader

reliability, images of 10 randomly selected subjects were read

independently by a musculoskeletal radiologist.

RESULTS: A total of 3360 bones were evaluated. Patients with RA had

significantly more erosions as well as higher scores for bone edema

and synovitis than healthy subjects. Age had a significant effect on

the number of erosions in both groups. However, when disease duration

was factored in, age became insignificant in RA patients. Erosion

number correlated with positive rheumatoid factor and higher

C-reactive protein values. The intraclass correlation coefficient

between the 2 readers was 0.76 for individual joints and 0.88 for

total scores. When having a single erosion was used as a positive test

for RA, the sensitivity of this test was 90%, but the specificity was

only 35%. Presence of bone edema provided 65% sensitivity and 82.5%

specificity. Eliminating the lunate from scoring for bone edema

increased the specificity to 87.5% while decreasing the sensitivity to

62.5%.

CONCLUSION: While MRI is a highly sensitive tool for identifying and

tracking the progression of erosions, erosions detected by MRI with

measures commonly used in a rheumatologist's office (no contrast,

imaging in 1 plane) provide low specificity for RA. Bone marrow edema

is the most specific MRI lesion for RA in this setting.

PMID: 19955056

http://www.ncbi.nlm.nih.gov/pubmed/19955056

Not an MD