Diagnostic value of paraclinical tests in multiple sclerosis: relative sensitivities and specificities for reclassification according to the Poser committee criteria.

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.