The yield of paraclinical tests was evaluated in a prospective study of 189 
consecutive patients referred for suspected multiple sclerosis (142 patients 
with multiple sclerosis, 47 non-multiple sclerosis patients on discharge). 
Patients were first classified according to the Poser criteria by the clinical 
findings. Subsequently, the results of paraclinical tests (cranial MRI, visually 
evoked potentials (VEPs), somatosensory evoked potentials by tibial nerve 
stimulation (SSEPs), motor evoked potentials (MEPs), and analysis of CSF for 
oligoclonal banding and IgG-index (CSF)) were taken into account. The percentage 
of reclassified patients (reclassification sensitivity, RS) was always lower 
than the percentage of abnormal results (diagnostic sensitivity, DS), and the 
divergence of RS v DS differed between the tests (60% v 84% in MRI, 31% v 77% in 
CSF, 29% v 37% in VEPs, 20% v 68% in MEPs, and 12% v 46% in SSEPs respectively). 
False reclassifications of non-multiple sclerosis patients to multiple sclerosis 
would have occurred with all tests (MRI: six of 47 patients, (reclassification 
specificity 88%); CSF: one (98%); VEPs: two (96%); MEPs: two (96%); SSEPs: four 
(91%); P < 0.05). Although MRI had superior diagnostic capacity, 57 of the 142 
patients with multiple sclerosis were not reclassified by the MRI result, 12 of 
whom were reclassified by CSF and 18 by one of the evoked potential (EP) 
studies. Of the 98 patients not reclassified by CSF, 53 were reclassified by MRI 
and 39 by EPs. The results suggest that for the evaluation of paraclinical tests 
in suspected multiple sclerosis, comparison of diagnostic sensitivities is 
inappropriate. In general, a cranial MRI contributes most to the diagnosis; 
however, due to its comparatively low specificity and its considerable number of 
negative results, EP or CSF studies are often useful to establish the diagnosis 
of multiple sclerosis.