TTP – Coach’s Corner
About Coach’s Corner
In the best of all worlds, clinical practice guidelines provide recommendations about diagnosis and treatment that are based on solid evidence from phase 3 clinical trials. In many cases, such evidence does not exist and recommendations are provided based on expert opinion. Even then, many questions pertinent to clinical care may be left out of guidelines. In Coach’s Corner, we aim to address some of these gaps by surveying the opinion of clinical experts from the TBP board of advisors in areas where there exists a gray zone. This exercise is not meant to provide definitive guidance for patient care, but rather is designed to highlight the importance of clinical experience and critical thinking in the decision making process.
The opinions presented in this case were obtained in May 2022, and may be subject to change as new evidence emerges.
Background: The ISTH guidelines for the diagnosis of thrombotic thrombocytopenic purpura (TTP) recommends assessing the pretest probability of TTP using clinical assessment (gestalt) and/or the risk assessment models like the PLASMIC or French score. In other words, the use of a clinical prediction rule is optional.
Question: Do you use the PLASMIC score to assess risk for TTP? If you use the PLASMIC score, do you have a cut-off value for instituting TPE?
Background: The British Society of Hematology recommends starting TPE “preferably within 4-8 hours of initial clinical diagnosis” regardless of the time of day.
We asked our experts:
Question: A patient presents to the ED of your hospital at 10 PM with high probability of having TTP. Your apheresis team is short-staffed and you cannot begin therapeutic plasma exchange (TPE) until 8 AM the next day. Would you send the patient to another hospital that has the means to carry out TPW overnight or would be comfortable waiting until the morning?
If the patient is stable, I would be okay with waiting until the next morning. In the interim, I would get the line (turnaround time ~ 1 hour) and plasma (turn around ~ 2 hours) ready. If the patient is unstable, they should get plasma infusion and transferred. I doubt that the NHS can pull off a new TPE in 4 hours!
While there is a possible trend to clinical benefit with TPE within 8 hours (see study), I wouldn’t transfer the patient. A hospital-to-hospital transfer would likely result in a delay to TPE of much greater than 10 hours. Rather, I would give the patient FFP and coordinate placement of central access so that TPE can begin right at 8 AM.
We have the capability of doing TPEs at all hours of the day EXCEPT midnight to 6 AM. This limitation relates to nurse staffing, but it takes ~ 6 hours to get a pheresis line placed. Thus, we’d work expeditiously to get a pheresis line placed and institute TPE ASAP when nursing is available. While waiting TPE we’d administer steroids and plasma.
Background: The 2020 ISTH guidelines on the treatment of thrombotic thrombocytopenic purpura (TTP) suggests using caplacizumab over not using caplacizumab for patients with immune TTP experiencing an acute event (first
event or relapse) (A conditional recommendation in the context of moderate certainty evidence.)
We asked our experts:
Question: Under what conditions would you treat a patient with newly diagnosed TTP with caplacizumab?
Background: The 2020 ISTH guidelines on the treatment of thrombotic thrombocytopenic purpura (TTP) suggests the addition of rituximab to corticosteroids and TPE over corticosteroids and TPE alone in patients with immune TTP experiencing their first acute event, the panel.
Question: Under what conditions would you treat a patient with newly diagnosed TTP with rituximab?