Time from suspected thrombotic thrombocytopenic purpura to initiation of plasma exchange and impact on survival: A 10-year provincial retrospective cohort study.

BACKGROUND:Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy (TMA) with significant morbidity and mortality. Guidelines recommend initiating plasma exchange within 4-8 h of suspected diagnosis. It is unclear what are real-world practice patterns and whether delays >8 h increases mortality. OBJECTIVES:To determine if delayed initiation of plasma exchange is associated with increased risk of death and complications. METHODS:In this retrospective cohort study, we evaluated the time from suspected diagnosis to plasma exchange in all adults presenting with suspected TTP to apheresis centres in Alberta, Canada (2008-2018). Among patients with acquired TTP, the association between delayed plasma exchange and risk of death was evaluated using Cox regression. RESULTS:Overall 190 episodes of suspected TTP were included among 163 individuals. Acquired TTP was confirmed in 61 patients. Inappropriate Emergency Department triage occurred in 59%. The median time from suspected diagnosis to first plasma exchange was 10.7 h; 59% had delayed plasma exchange >8 h, among whom plasma infusion was administered in only 45%. 36% of suspected TTP and 13% of confirmed TTP patients died. Delayed plasma exchange between 8 and 24 h was not associated with a significantly higher risk of death (adjusted hazards ratio; aHR 0.63, 95% CI 0.08-4.83) in confirmed TTP. On the other hand, the risks of death (aHR 1.40, 95% CI 0.20-9.79) and major thrombotic events (aHR 2.9, 95% CI 0.6-12.8) were markedly increased with >24 h delay. CONCLUSIONS:Our study demonstrated that TTP care in a real-world setting is discordant with expert guidelines due to multiple barriers. There is a gradient of increased mortality risk and thrombotic complications with longer treatment delays, although the study is likely underpowered.