Estimating Long-Term Organ Damage Risk in Patients with Congenital Thrombotic Thrombocytopenic Purpura Receiving Recombinant ADAMTS13 Prophylaxis: A Structured Expert Elicitation Study

Longitudinal real-world data in congenital thrombotic thrombocytopenic purpura (cTTP) are scarce. Structured expert elicitation (SEE) was conducted to estimate the projected risk of long-term organ damage in children and adolescents and in adult patients with cTTP receiving recombinant ADAMTS13 (rADAMTS13) prophylaxis, without history of organ damage. Six UK clinicians with experience in managing cTTP provided individual judgments via an online SEE survey. The probability of developing ≥ 1 long-term organ damage outcomes, including major organ events such as stroke/transient ischemic attack, myocardial infarction, and chronic kidney disease, at predefined ages was estimated. Responses were collected using the quartile method and combined via linear opinion pooling. In children and adolescents, median (95% credible interval) estimated cumulative long-term organ damage projected risks were 3.25% (1.09–20.26%) by age 15 years, 4.48% (0.86–16.11%) by 20 years, and 5.76% (0.96–19.20%) by 25 years. In adults, estimated risks were 4.85% (0.59–16.96%) by 45 years and 7.42% (1.47–29.29%) by 55 years. Experts consistently projected lower long-term risks of organ damage with continuous rADAMTS13 prophylaxis, although these estimates remain hypothesis-generating. These expert-derived estimates provide structured insights into potential long-term outcomes associated with rADAMTS13 prophylaxis, which can inform future research, health technology assessments, and evidence-generation efforts in cTTP. Prospective empirical studies are required to confirm the findings. Graphical Abstract available for this article.