PB0298 - A Systematic Review of the Current Epidemiology of Immune-Mediated and Congenital Thrombotic Thrombocytopenic Purpura caused by Severe ADAMTS13 Deficiencies

Background: Immune-mediated (iTTP) and congenital (cTTP) thrombotic thrombocytopenic purpura are rare clotting disorders caused by either an acquired or an inherited deficiency in the von Willebrand factor-cleaving enzyme ADAMTS13.

Aims: To synthesize knowledge on the epidemiology of iTTP and cTTP worldwide.

Methods: A systematic review (PROSPERO CRD42020172273) of observational studies published from January 01, 2010 to February 06, 2020 was conducted following the PICOTS (population, intervention/exposure, comparator, outcomes, time period, study type) approach. Target population was overall TTP, iTTP, and cTTP. Outcomes of interest included incidence, prevalence, patient characteristics at diagnosis, and mortality. Information sources were literature searches (Ovid® MEDLINE and Embase), pragmatic searches (Google, Google Scholar, congresses, clinical societies, and patient organizations), and snowballing. Case reports, case series, clinical trials, and non-clinical/experimental studies were excluded. Study selection and data extraction were conducted independently by 2 reviewers.

Results: A total of 153 eligible sources, mainly from Europe and North America, were included in the review (iTTP specific, n=47; cTTP specific, n=11; iTTP and cTTP, n=2; unspecified, n=93). Table 1 shows overall prevalence and incidence of TTP. Median age at cTTP diagnosis ranged from 16.7 to 18.7 years in two multinational studies, while in another study disease onset generally occurred either during early childhood (median age at diagnosis 3.5 years) or in adulthood (median age at diagnosis 31 years). For iTTP, patients typically experienced their first episode in their 40s (9 sources). Mortality associated with cTTP was reported between 0 and 8.3% with different populations and follow-up periods in 7 studies, mainly involving European countries. Mortality associated with iTTP was highly varied across 29 studies, with estimates up to 15.2% in France, 12.8% in the US, and 30% in China.

Conclusion(s): Data on the epidemiology of cTTP are limited. In addition, data from Asia and the Middle East are limited for both iTTP and cTTP.