Diagnostic uncertainty during the transition to secondary progressive multiple sclerosis: Multicenter study in Argentina

Background: A period of diagnostic uncertainty often characterizes the clinical transition from relapsing to secondary progressive multiple sclerosis (SPMS).

Objective: The aim of this study was to describe the length of time required to reclassify relapsing-remitting MS (RRMS) patients who have clinically transitioned to SPMS (diagnosis uncertainty).

Methods: This is a retrospective multicenter cohort study conducted in Argentina, identifying in every center all patients with diagnosis of MS who transitioned from RRMS to SPMS during the follow-up. We identified the dates of the last definitive RRMS and first definitive SPMS diagnoses for diagnostic uncertainty. The time required to reclassify RRMS who transitioned to SPMS and the time from disease onset to reclassify SPMS were calculated using the Kaplan-Meier method.

Results: A total of 170 patients were included, where the mean age at disease onset (first symptom) was 36 ± 6 years; the length of time required to reclassify RRMS patients who transitioned to SPMS was 3.3 ± 1.1 years (range = 1-7 years); and the time from disease onset to classify SPMS was 19.4 ± 8.5 years (range = 16-35 years).

Conclusion: A period of diagnostic uncertainty regarding the transition from RRMS to SPMS was present in many of our patients, with a mean time of 3.3 years.