Diagnostic delay of multiple sclerosis: prevalence, determinants and consequences

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.