Accuracy of magnetic resonance imaging for the diagnosis of multiple sclerosis

The accuracy of magnetic resonance imaging (MRI) is not sufficient to rule in or rule out a diagnosis of MS with a high degree of certainty, finds a study published online by the British Medical Journal.

MRI has been adopted in England and Wales by the National Institute for Health and Clinical Excellence (NICE) as part of the recommended criteria for diagnosing multiple sclerosis. Although its accuracy has been assessed, the evidence has not previously been systematically assessed.

Researchers analysed 29 studies to assess the accuracy of magnetic resonance imaging criteria for the early diagnosis of multiple sclerosis in patients with suspected disease. Each study compared MRI criteria to a reference standard for the diagnosis of multiple sclerosis. The average duration of follow-up ranged from seven months to 14 years.

Considerable weaknesses existed in the studies included in the review, and studies with methodological flaws overestimated the diagnostic accuracy of MRI.

Only two studies followed patients for more than 10 years, and these suggested that the role of magnetic resonance imaging either in ruling in or ruling out multiple sclerosis is limited. Patients with a first attack suggestive of MS have around a 60% probability of developing MS, this is increased to between 75 and 84% in those with a positive MRI scan and decreased to between 43 and 57% in those with a negative scan over 10-14 years.

The results suggest that use of magnetic resonance imaging to confirm multiple sclerosis on the basis of a single attack of neurological dysfunction may lead to over-diagnosis and over-treatment.

"There is a real danger of giving patients a serious diagnosis which will affect their lives but may turn out to be incorrect later on," says Penny Whiting.

Dr Jonathan Sterne adds: "Neurologists should discuss potential consequences of false positive and false negative magnetic resonance imaging results with their patients."