BACKGROUND: Early diagnosis and treatment of patients with multiple sclerosis (MS) are associated with better outcomes; however, diagnostic delays remain a major problem. OBJECTIVE: Describe the prevalence, determinants and consequences of delayed diagnoses. METHODS: This single-centre ambispective study analysed 146 adult relapsing-remitting MS patients (2016-2021) for frequency and determinants of diagnostic delays and their associations with clinical, cognitive, imaging and biochemical measures. RESULTS: Diagnostic delays were identified in 77 patients (52.7%), including 42 (28.7%) physician-dependent cases and 35 (24.0%) patient-dependent cases. Diagnosis was delayed in 22 (15.1%) patients because of misdiagnosis by a neurologist. A longer diagnostic delay was associated with trends towards greater Expanded Disability Status Scale (EDSS) scores (B = 0.03; p = 0.034) and greater z-score of the blood neurofilament light chain (B = 0.35; p = 0.031) at the time of diagnosis. Compared with patients diagnosed at their first clinical relapse, patients with a history of >1 relapse at diagnosis (n = 63; 43.2%) had a trend towards greater EDSS scores (B = 0.06; p = 0.006) and number of total (B = 0.13; p = 0.040) and periventricular (B = 0.06; p = 0.039) brain lesions. CONCLUSION: Diagnostic delays in MS are common, often determined by early misdiagnosis and associated with greater disease burden.

• Keywords
• Delayed diagnosis, brain lesion, cerebrospinal fluid, disability, magnetic resonance imaging, misdiagnosis, multiple sclerosis, neurofilament,
• MeSH
• Adult MeSH
• Humans MeSH
• Magnetic Resonance Imaging MeSH
• Brain pathology   MeSH
• Delayed Diagnosis MeSH
• Prevalence MeSH
• Recurrence MeSH
• Multiple Sclerosis, Relapsing-Remitting * diagnosis   epidemiology   pathology   MeSH
• Multiple Sclerosis * diagnosis   epidemiology   pathology   MeSH
• Check Tag
• Adult MeSH
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH