A concept-focused literature review was conducted via PubMed to identify qualitative, patient-centered research, such as focus groups, interviews, surveys focusing on limitations and QOL impacts experienced by PwMS. A total of 225 abstracts were screened, 34 were selected for full article review, and 12 ultimately included for concept extraction. Hidden problems were defined as symptoms and QoL impacts beyond relapses and disability as measured by Expanded Disability Status Scale (EDSS), and were organized by domain into a conceptual model. A gap analysis was performed to assess whether COAs used in MS include the identified concepts.

Almost 100 concepts were extracted covering function (n=5 domains; cognition, energy/sleep, sexual, emotional, physical), daily life (n=4 domains; relationships, social life, work, daily activities) and sense of self (n=2 domains; self-efficacy, adaptive behaviour). No MS COA comprehensively assess all domains. MS Impact Scale (MSIS-29) and Fatigue Severity Scale (FSS) only measure 3 and 1 domains respectively. MS Quality of Life Inventory (MSQLI) and MSQoL-54 are the most comprehensive, measuring seven domains each.

Existing COAs fail to capture the full disease experience of PwMS and therefore may not measure meaningful effect of MS therapies either. Existing COAs could be modified, or new tools created, to reflect the most salient hidden MS problems. An artificial intelligence (AI) approach combing holistic screening and assessment, could also address current gaps in measurement.