To describe the natural history of a condition or disease. To describe the natural history of a condition or disease. To determine effectiveness or cost effectiveness of treatments/services and/or health care products. To measure or monitor safety and harm. To measure quality of care.
According to the NMSS, attacks or flare-ups of symptoms only qualify as exacerbations if: 1  they occur at least 30 days from an earlier flare-up. 2  symptoms last for 24 hours or longer.
Relapsing-remitting, where symptoms may fade and then recur at random for many years. The disease doesn't advance during the remissions. Most people who develop MS have a relapsing-remitting course. In 8 to 9 out of 10 people with this course of MS, the relapsing-remitting phase lasts about 20 years.