Objective: To evaluate the clinical significance of the 2005 modified imaging criteria for dissemination in time in multiple sclerosis stating that detection of a new T2 lesion appearing at any time compared with a reference scan done at least 30 days after the onset of a clinically isolated syndrome implies dissemination in time.
Methods: We included consecutive patients younger than 50 years examined at our center within 3 months of a clinical syndrome suggestive of central nervous system demyelination of the type seen in multiple sclerosis and followed for at least 3 years. We classified patients into one of two groups, according to the timing when reference scan was performed: less than 30 days and at least 30 days after symptom onset. We analyzed the interaction in time to relapse between timing of reference scan and new T2 lesion effect.
Results: A total of 218 patients were included. The hazard ratio (95% confidence interval) of this interaction was 0.90 (0.31-2.62) (or 1.02 (0.27-3.91) in patients with dissemination in space).
Conclusions: We conclude that new T2 lesions increased relapse risk regardless of timing of the reference scan, supporting the use of scans performed at any time within 30 days of symptom onset for dissemination in time demonstration.