Higher health care use before a clinically isolated syndrome with or without subsequent MS

To establish whether a unique multiple sclerosis (MS) prodrome exists by comparing health care utilization in the five-year period before initial presentation with optic neuritis (ON) or transverse myelitis (TM) among those who were and were not subsequently diagnosed with MS.

Using population-based administrative health data we conducted a retrospective cohort study in three Canadian provinces. We identified individuals with a clinically isolated syndrome (ON or TM), who were eventually diagnosed with MS (CIS-MS) or not (CIS-non MS), and a control cohort matched on age, sex and region without a CIS. We compared rates of hospitalization, physician services use and prescription drug use in the five years before the first ON or TM claim (labeled years -1,-2,-3,-4,-5) using negative binomial regression models adjusted for age, sex, socioeconomic status and index year.

We identified 1,155 CIS-MS cases, 20,638 CIS-non MS cases, and 108,726 matched controls. Compared to matched controls, the CIS-MS cohort had a higher hospitalization rate (years -5 and -1), physician visits (all years) and prescription drug use (years -4 and -1). Compared to matched controls, the CIS-non MS cohort had a higher rate of hospitalizations (all years), physician visits (all years) and prescription drug use (all years).

Health care use was higher in individuals with a CIS than without a CIS in the five years before an incident demyelinating event, regardless of whether they were subsequently diagnosed with MS. This suggests that there is a prodromal period before CIS which is not unique to MS.