Patients' records review procedure and sampling strategies. The medical records, administrative data, laboratory and diagnostic tests reports were screened by 3 authors (HS, NS, AE) and these data were extracted in a standard electronic form according to Kasr Alaini Multiple Sclerosis Unit (KAMSU) registry.
An assigned coordinator from each center was requested to facilitate data collection from site-specific records. In cases of incomplete documentation or unclear information, verification was done by on-site data coordinator either by phone contact or face-to-face interview with the patients, whether during the routine follow up or in an unscheduled visit.
Several measures were taken to ensure the confidentiality of the collected information. No patient names were included in the database presented by site coordinator, and the study staff signed a confidentiality agreement for non-disclosure.
