THE ACCURACY OF MAGNETIC-RESONANCE-IMAGING IN PATIENTS WITH SUSPECTEDMULTIPLE-SCLEROSIS

Objective.-To design and implement a methodologically rigorous study t o examine the accuracy of magnetic resonance imaging (MRI) in a patien t population clinically suspected of having multiple sclerosis (MS). D esign and Setting.-Three hundred three patients, who were referred to two university medical centers because of the suspicion of MS, underwe nt MRI of the head and double-dose, contrast-enhanced computed tomogra phy (CT) of the head. The images were read by two observers individual ly and without knowledge of the clinical course or final diagnosis. Pa tients were followed up for at least 6 months and reevaluated clinical ly with subsequent neurological examination. Final diagnosis (MS or no t 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 exc luded to avoid incorporation bias. Diagnostic accuracy was assessed us ing 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-operati ng characteristic curve for MS was 0.82 (compared with 0.52 for CT) in dicating 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, es pecially in patients clinically designated as ''probable MS'' before t esting. However, MRI of the head was negative for MS in 25% and equivo cal in 40% of the patients considered to have MS by the diagnostic rev iew committee (sensitivity, 58%). Conclusions.-Magnetic resonance imag ing of the head provided assistance in the diagnosis of MS when lesion s were visualized. Its ability far exceeded imaging with double-contra st CT. The sensitivity and, therefore, the predictive value of a negat ive MRI result for MS were, however, not sufficiently high for a norma l MRI to be used to conclusively exclude the diagnosis of MS.