MRI of healthy hands contribute to validation of MRI in RA

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Rheumawire

May 4, 2004

MRI of healthy hands contribute to validation of MRI in RA

Hvidovre, Denmark - Although MRI is increasingly being used in

rheumatoid arthritis (RA), questions about this imaging modality remain.

Among them is the issue of specificitythat is, are the changes picked up

by MRI in patients with RA really signs of disease?

Addressing this question is a new study from Denmark, which is one of

the first to look at MRI imaging of hands in healthy people. In the

April 2004 issue of Arthritis & Rheumatism [1], the researchers report

that in these healthy subjects, MRI changes resembling mild synovitis or

small bone erosions were found " occasionally, " but other changesearly

enhancement in the synovial compartment on dynamic MRI, enhancement

within bone-erosion-like changes, and signs of bone-marrow edemawere

seen only rarely or were absent. " These signs that may thus prove to be

very specific in the distinction between arthritic and normal joints, "

say Dr Bo Ejbjerg and colleagues (Copenhagen University, Hvidovre,

Denmark).

Ejbjerg describes the study as " an important step in the validation

process " for the use of MRI as an imaging modality in rheumatoid

arthritis. " It is important to investigate the sensitivity and

specificity of different MRI approaches, because the choice of a

measure's cutoff level between normal and abnormal is often a trade-off

between sensitivities and specificities, " he tells rheumawire.

Few previous MRI studies have included healthy subjects, and these

studies had other primary aims and also used a variety of MRI

techniques. Nevertheless, the latest findings are in line with what has

been reported previously, Ejbjerg says. He also emphasized that his team

used MRI according to the latest consensus recommendations from Outcome

Measures in Rheumatology (OMERACT), obtaining images in several planes,

with and without the use of contrast medium (which increases the ability

to detect arthritic changes, especially synovitis), and they also used

dynamic MRI.

MRI images were taken of the wrist and the second to fifth

metacarpophalangeal (MCP) joints of the dominant hand in each subject

(n=28). In addition, each subject also had the same hand and wrist

x-rayed (in 3 positions), was examined by a rheumatologist for joint

swelling and tenderness, and had a blood sample evaluated for

biochemical evidence of disease (C-reactive protein [CRP] and rheumatoid

factor, IgM-RF).

One of the most important findings of the study was that there was no

bone-marrow edema in healthy subjects, Ejbjerg comments. This is a

frequent finding in RA patients and is associated with an increased (up

to 6.5-fold) risk of developing erosive disease in patients with early

disease. This indicates that the presence of bone-marrow edema is an

indicator of a " real pathologic event, " the researchers write.

The bone-marrow edema is not disease-specific since it is a well-known

finding in osteoarthritis and posttraumatic conditions as well as RA,

the researchers note. " But the patient's disease history and clinical

examination would have already differentiated between these conditions,

even before MRI was carried out, " Ejbjerg points out.

" The absence of early synovial enhancement in healthy subjects is also

of major importance, since this feature helps in the distinction between

arthritis joint changes and normal joints, " Ejbjerg adds.

All of the changes that appeared on MRI in the healthy hands were low

grade and were found in only a few of the subjects. Ejbjerg comments

that these changes can be considered as " background noise " and that they

" represent the gap between real findings and a hypothetical 100%

specificity. "

He notes that no test in rheumatology is 100% specific, including x-ray

and blood testing for biochemical abnormalities. " Sometimes you see

something, eg, a high titer of antibodies, in a person with no specific

disease. " To optimally minimize this in future studies of MRI imaging in

healthy subjects, Ejbjerg suggests prescreening with x-ray and tests for

biochemical abnormalities and excluding subjects with any findings.

MRI shows up 2 types of low-grade changes in healthy hands:

Erosionlike changes were seen in 5 of 224 MCP-joint bones (2.2%)

and in 7 of 420 wrist-joint bones (1.7%), but only 1 of these showed

enhancement on postcontrast images.

Synovitislike changes were found in 10 of 112 MCP joints (in 7

subjects) and in 8 of 84 wrist areas (in 6 subjects, with an overlap of

4 subjects between the 2 groups).

Conventional radiography showed changes classified as bone erosions in 2

subjectsin 1 of 224 MCP-joint bones (0.4%) and in 1 of 420 wrist-joint

bones (0.2%). Neither of these 2 subjects showed up erosionlike changes

on MRI, Ejbjerg tells rheumawire.

The results of the clinical and biochemical examinations were normal in

all the subjects, except for 3 with biochemical abnormalities. One

subject had slightly elevated levels of both IgM-RF and CRP, and this

subject had synovitislike changes in 2 MCP joints and was also the only

subject who showed an erosionlike lesion with enhancement on

postcontrast MRI. The other 2 subjects had slightly elevated levels of

CRP, and both had synovitislike changes in the second and third MCP

joints and in the wrist joints.

Between them, these 3 subjects (11% of the study group) accounted for

60% of the erosionlike changes in MCP bones and 28.6% of those in the

wrist bones and for 44.4% of all the synovitislike changes. None of

these 3 subjects reported any joint problems, but together these

findings may suggest that some of them may have subclinical arthritis,

the researchers comment.

Ejbjerg adds that these subjects were asked to visit their general

practitioner if they experienced any arthritis joint complaints. If the

GPs find any suspicion on clinical examination, they can refer these

patients to the early arthritis clinic, where they will be followed up

by MRI and standard clinical examinations.

Zosia Chustecka

Source

1. Ejbjerg B, Narvestad E, Rostrup E, et al. Magnetic resonance imaging

of wrist and finger joints in healthy subjects occasionally shows

changes resembling erosions and synovitis as seen in rheumatoid

arthritis. Arthritis Rheum 2004 Apr; 50(4):1097-106.

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