Prodrome in relapsing-remitting and primary progressive multiple sclerosis

Background and purpose The multiple sclerosis prodrome remains poorly understood. We aimed to examine the prodrome in people with relapsing remitting multiple sclerosis at onset (RMS) and primary progressive multiple sclerosis (PPMS). Methods We conducted a matched cohort study using clinical and linked health administrative data in two Canadian provinces. We identified people with RMS, PPMS and age- sex- and geographically-matched population controls, and compared the number of physician encounters (total number, per International Classification of Diseases chapter, and per physician speciality) in the five years before symptom onset. Negative binomial regression models were sex, age, socioeconomic status and calendar year adjusted. Results We identified 1887 RMS, 171 PPMS cases, and 9837 matched population controls. No difference existed in the total number of encounters in the five years before index between RMS and PPMS, or between the phenotypes and their respective controls. Compared to RMS cases, PPMS cases had more nervous system-related encounters (adjusted rate ratio, 3.00; 95% confidence interval, 1.06-8.49) and fewer encounters with dermatologists (adjusted rate ratio 0.53; 95% confidence interval, 0.30-0.96). Conclusion Findings suggest that people with RMS and PPMS may both experience a prodrome, although aspects may differ.