title: Conversion from radiologically isolated syndrome to multiple sclerosis.
abstract: BACKGROUND
  The aim of this study was to estimate the conversion rate from radiologically isolated syndrome (RIS) to definite multiple sclerosis (MS).
  
  
  METHODS
  During a mean (standard deviation [SD]) follow-up period of 17.4 (5.4) (range 8-29) months, 25 subjects with RIS and without neurological symptom aged 22-45 year from a single-center have been examined for the occurrence of definite MS. The mean (SD) age of participants was 35.1 (6.2) years at first brain magnetic resonance imaging (MRI). The definite MS were assessed using the revised McDonald's criteria (2010).
  
  
  RESULTS
  Six of 25 patients developed clinical symptom consistent with criteria for definite MS. The conversion rate from RIS to definite MS was 1.5 (95% confidence interval [CI] 0.54, 3.17) per 100 person-months based on 480 person-months of follow-up. Multivariate analysis revealed that presence of contrast-enhancing lesions on the initial MRI was marginally significantly associated with MS (hazard ratio 1.83, 95% CI 0.98, 3.45, P = 0.060).
  
  
  CONCLUSIONS
  This is the first estimate of conversion rate from RIS to definite MS in Iran. The conversion rates from RIS to definite MS in these participants are high and intensive follow-up and intervention strategies are recommended for these high-risk individuals. A larger study is warranted to assess this risk in greater detail.
authors.affiliation: Isfahan Multiple Sclerosis Society, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Masoud
authors.initials: M
authors.lastname: Etemadifar
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Mohsen
authors.initials: M
authors.lastname: Janghorbani
authors.affiliation: Isfahan Multiple Sclerosis Society, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Mohammad Mehdi
authors.initials: MM
authors.lastname: Koushki
authors.affiliation: Isfahan Multiple Sclerosis Society, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Etemadifar
authors.affiliation: Isfahan Multiple Sclerosis Society, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Mahboobeh Fereidan
authors.initials: MF
authors.lastname: Esfahani
keywords: Conversion rate; Iran; longitudinal study; multiple sclerosis; predictors; radiologically isolated syndrome