This was an observational retrospective cohort study using electronic medical records (EMRs) to study immunoglobulin levels over time among patients with relapsing forms of multiple sclerosis (MS) newly initiating anti-CD20 monoclonal antibody treatment in clinical practice.

The index date was defined as the date of anti-CD20 drug initiation during the study period. The baseline period was defined as 12 months prior to the index date.

Inclusion criteria:

• Patients aged 18 years or older at index.
• Patients with RMS, including clinically isolated syndrome (CIS), relapsing-remitting multiple sclerosis (RRMS), and secondary progressive multiple sclerosis (SPMS) at the time of initiating anti-CD20 treatment.
• Newly initiated anti-CD20 treatment after March 2017 (no history of anti-CD20 therapy at any time in medical record before this date) to the latest data cutoff (November 2022).
• Patients with at least one documented IgG lab value pre- and post-anti-CD20 drug initiation.

Exclusion criteria:

• Patients with diagnosis of primary progressive multiple sclerosis (PPMS) prior to anti-CD20 treatment.
• Participated in an anti-CD20 drug clinical trial during the study period.

This was a retrospective, noninterventional cohort study.