Application of the new McDonald criteria to patients with clinically isolated syndromes suggestive of multiple sclerosis
Dalton CM, Brex PA, Miszkiel KA, Hickman SJ, MacManus DG, Plant GT, Thompson AJ, Miller DH.;
Commented by , 19 Aug 2002
Background
During the last decade new opportunities for the treatment of Multiple Sclerosis (MS) have emerged, and recently interest has focused on the benefit of early medication.
Traditionally, the diagnosis has been based on the clinical evidence of dissemination in time and space (Poser’s criteria), which might postpone counseling and potential therapeutic intervention. Since approximately 60% of patients with clinically isolated syndromes suggestive of MS has disseminated lesions on brain MRI, new diagnostic criteria from the International Panel of McDonald and colleagues have incorporated MRI in order to ensure an early diagnosis.
Aim
To address the diagnostic value of the new McDonald criteria compared to the Poser criteria in MS.
Method
The study was prospective and incorporated 119 patients with clinically isolated syndromes. All patients were assessed at baseline, 3 months, 1 year, and 3 years. Disability was recorded (EDSS) and MRI (1,5 Tesla) of the brain was performed acquiring PD, T2 and T1-weighted images as well as gadolinium before imaging.
MRI of the spinal cord was performed at baseline and after 1 and 3 years. Additionally, cord atrophy was measured at baseline and after 1 year. The specificity, sensitivity, positive and negative predictive value, and accuracy of the new criteria (applied retrospectively) for the development of clinically definite MS were assessed.
Results
At 3 months, 21% of patients had MS with the McDonald criteria, whereas only 7% had developed clinically definite MS with the Poser criteria. After 1 year, the corresponding figures were 48% and 20%, and after 3 years 58% and 38%.
The development of MS with the new MRI criteria after 1 year had a high sensitivity (83%), specificity (83%), positive predictive value (75%), negative predictive value (89%), and accuracy (83%) for clinically definite MS at 3 years.
Discussion
The earliest clinical event in most MS patients is a clinically isolated syndrome, and the presence of multifocal MRI abnormalities increases the risk of developing clinically definite MS.
Using the new criteria revealed that half the patients had a diagnosis of MS after 1 year, whereas only one fifth did with the traditional criteria. Spinal cord imaging did not contribute much towards early diagnosis of patients who developed MS with the new criteria, presumably because imaging was obtained less frequently in the cord and also due to the fact that new lesions occur more often in the brain.
The diagnostic accuracy was high although CSF findings were not included in the study. The study showed a high sensitivity, and more importantly a high specificity after 3 months and 1 year and especially after 3 years. Since the authors also found a high positive predictive value it is concluded that the new criteria are clinically relevant.