In 1997, the Canadian Apheresis Group reviewed data on 103 416 plasma exchange procedures that had been collected since 1980.
Striking changes occurred over time in the frequency of use of apheresis, particularly for thrombotic thrombocytopenic purpura,
myasthenia gravis, rheumatoid arthritis, and multiple sclerosis. In most instances, changes in the frequency of apheresis
use correlated closely with published evidence on efficacy.