The accuracy of magnetic resonance imaging in patients with suspected multiple sclerosis. The Rochester-Toronto Magnetic Resonance Imaging Study Group
A. I. Mushlin, A. S. Detsky, C. E. Phelps, P. W. O'Connor, D. K. Kido, W. Kucharczyk, D. W. Giang, C. Mooney, C. M. Tansey and W. J. Hall
Department of Community and Preventive Medicine, University of Rochester, NY.
OBJECTIVE--To design and implement a methodologically rigorous study to
examine the accuracy of magnetic resonance imaging (MRI) in a patient
population clinically suspected of having multiple sclerosis (MS). DESIGN
AND SETTING--Three hundred three patients, who were referred to two
university medical centers because of the suspicion of MS, underwent MRI of
the head and double-dose, contrast-enhanced computed tomography (CT) of the
head. The images were read by two observers individually and without
knowledge of the clinical course or final diagnosis. Patients were followed
up for at least 6 months and reevaluated clinically with subsequent
neurological examination. Final diagnosis (MS or not MS) was made by a
panel of neurologists on the basis of the clinical findings at
presentation, those that developed during follow-up, and other diagnostic
tests. The results of the imaging procedures were excluded to avoid
incorporation bias. Diagnostic accuracy was assessed using
receiver-operating characteristic analysis and likelihood ratios.
RESULTS--Magnetic resonance imaging of the head was considerably more
accurate than CT in diagnosing MS. The area under the receiver-operating
characteristic curve for MS was 0.82 (compared with 0.52 for CT) indicating
that MRI was a good but not definitively accurate test for MS. A "definite
MS" reading on an MRI of the head was specific for MS (likelihood ratio,
24.9) and essentially established the diagnosis, especially in patients
clinically designated as "probable MS" before testing. However, MRI of the
head was negative for MS in 25% and equivocal in 40% of the patients
considered to have MS by the diagnostic review committee (sensitivity,
58%). CONCLUSIONS--Magnetic resonance imaging of the head provided
assistance in the diagnosis of MS when lesions were visualized. Its ability
far exceeded imaging with double-contrast CT. The sensitivity and,
therefore, the predictive value of a negative MRI result for MS were,
however, not sufficiently high for a normal MRI to be used to conclusively
exclude the diagnosis of MS.
