Active and non-active secondary progressive multiple sclerosis patients exhibit similar disability progression: results of an Italian MS registry study (ASPERA).

'Active' and 'non-active' secondary progressive MS (SPMS) have distinct pathophysiological mechanisms and clinical characteristics, but there is still no consensus regarding the frequency of these MS forms in the real-world setting. We aimed to evaluate the frequency of 'active' and 'non-active' SPMS in a large cohort of Italian MS patients and the differences in terms of clinical and MRI characteristics and disease progression. This multicenter study collected data about MS patients who have transitioned to the SP form in the period between 1st January 2014 and 31st December 2019 and followed by the MS centers contributing to the Italian MS Registry. Patients were divided into 'active SPMS' and 'non-active SPMS', based on both reported MRI data and relapse activity in the year before conversion to SPMS. Out of 68,621, 8,316 (12.1%) patients were diagnosed with SPMS. Out of them, 872 (10.5%) were classified into patients with either 'active' or 'non-active' SPMS. A total of 237 were classified into patients with 'active SPMS' (27.2%) and 635 as 'non-active SPMS' (72.8%). 'Non-active SPMS' patients were older, with a longer disease duration compared to those with 'active SPMS'. The percentages of patients showing progression independent of relapse activity (PIRA) at 24 months were similar between 'active' and 'non-active' SPMS patients (67 [27.4%] vs 188 [29.6%]; p = 0.60). In the 'active' group, 36 (15.2%) patients showed relapse-associated worsening (RAW). Comparison of the survival curves to EDSS 6 and 7 according to disease activity did not show significant differences (p = 0.68 and p = 0.71). 'Active' and 'non-active' SPMS patients had a similar risk of achieving disability milestones, suggesting that progression is primarily attributed to PIRA and only to a small extent to disease activity.