Systematic Assessment of Medical Diagnoses Preceding the First Diagnosis of Multiple Sclerosis.

Our analyses suggest that patients with MS are frequently not diagnosed at their first demyelinating event but often years later. Symptoms and physician encounters before MS diagnosis seem to be related to already ongoing disease rather than a prodrome. The observed association of upper respiratory tract infections with lower ORs of MS diagnosis suggests a link between protection from infection and MS that however needs to be validated and further investigated.