Background: In multiple sclerosis (MS), disability may accumulate in the form of deterioration linked to relapses, known as Relapse-Associated Worsening (RAW), or through a continuous progression unaffected by relapse activity, termed Progressive Independent of Relapse Activity (PIRA).
Objectives: To investigate PIRA's baseline predictors at the time of MS diagnosis and the contributions of PIRA versus RAW to the long-term clinical outcomes in secondary progressive MS (SPMS) patients.
Methodology: A retrospective cohort study was conducted at Nasser institute hospital on 150 patients with SPMS. Baseline and clinical data were collected during MS diagnosis, progression data during the disease course, and further outcome data. Also, different disability scores associated with PIRA and RAW were performed.
Results: Of 150 SPMS patients, 90 had PIRA, and 60 had RAW. Only age and type of relapses before starting disease modifying drugs (DMDs) showed significant differences between the groups. Patients with PIRA had higher mean age (40.1 ± 5.1 vs. 38.3 ± 5.43, p = 0.04) and fewer vision relapses than patients with RAW (34.4% vs. 51.7%, respectively p = 0.036). Moreover, no differences were found in magnetic resonance imaging (MRI) findings, including lesions and oligoclonal bands. There were significant associations between PIRA and poor long-term outcomes indicated by expanded disability status scale (EDSS), simple digit modalities test (SDMT), and 25-foot timed walk test (25FWT).
Conclusion: After the initial diagnosis of PIRA manifesting multiple sclerosis is prevalent among patients who develop secondary progression and indicates an unfavorable long-term prognosis. However, the prediction of PIRA is challenging, and further prospective research is warranted.