The Plasma Large-Volume Exchange RCT

Thrombotic thrombocytopenia purpura / hemolytic uremic syndrome (TTP/HUS) is a rare, life-threatening disorder. TTP/HUS causes multiple blood clots to form, which prevents blood from reaching the brain and kidneys. TTP/HUS affects 3-5 people per million per year. Anyone can develop TTP/HUS, but it is most common among 30-40 year olds, and women are twice as likely as men to acquire the condition. TTP/HUS sometimes develops as a result of medication use, pregnancy or cancer; however, for the majority of patients (80%) the cause of TTP/HUS is unknown. In 1991, researchers discovered that plasma exchange was superior to plasma infusion in treating idiopathic TTP/HUS. During plasma exchange the patient\'s blood plasma is removed and replaced with healthy blood plasma. Without plasma exchange, the survival rate for TTP/HUS is extremely low, with fewer than 5% of patients surviving. Treating TTP/HUS with plasma exchange improved the survival rate to 80%. Although this represents a dramatic improvement, researchers are still searching for methods to improve survival. No major advances in treating TTP/HUS have occurred in the past 20 years. Recent research suggests that high-dose plasma exchange may improve the survival of TTP/HUS patients. The investigators will conduct a randomized controlled trial to test whether treating TTP/HUS patients with high-dose versus standard-dose plasma exchange improves the treatment response. The investigators will recruit 150 patients with TTP/HUS from 9 centres across Canada over three years. The investigators will evaluate whether high-dose plasma exchange improves the treatment response, survival, and whether it reduces the number and volume of plasma exchange procedures and duration of hospital stay.