Grossman, Brenda J

ABSTRACTImmune thrombotic thrombocytopenic purpura (iTTP) is characterized by microangiopathic hemolytic anemia, thrombocytopenia, and microvascular occlusion secondary to acquired ADAMTS13 deficiency. Contemporary data regarding iTTP treatment practices in the US, including the use of caplacizumab, are lacking. We aimed to characterize the demographics and therapies, including medications and apheresis practices, in patients with iTTP in the US. We retrospectively analyzed iTTP cases at 15 sites in the US that provide comprehensive care for patients with iTTP. The time‐period assessed was from January 1, 2017 to December 31, 2021. Our primary objective was to analyze data by iTTP episode, inclusive of initial episodes and relapses. A total of 390 iTTP episodes were reported for 280 unique individuals (187 females, 93 males). Thirty‐day mortality was 3.7% (14/374), and 6‐month mortality was 7.4% (27/367). TPE details were reported for 343 episodes, among which 261 underwent at least one procedure (median 6, IQR 3–11). Among the 261 episodes with at least one therapeutic plasma exchange (TPE) performed, 82.0% (214/261) used only plasma. Caplacizumab was used either alone or in combination with other agents in 43 (11.0%) episodes. Management strategies for iTTP remain varied across centers in the US, with a variety of combinations for TPE replacement fluids and therapeutic agents, as well as limited use of caplacizumab. Further research and standardization of treatment regimens may further reduce mortality in this condition.

Background and ObjectivesABO blood group may affect risk of SARS‐CoV‐2 infection and/or severity of COVID‐19. We sought to determine whether IgG, IgA and neutralizing antibody (nAb) to SARS‐CoV‐2 vary by ABO blood group.Materials and MethodsAmong eligible convalescent plasma donors, ABO blood group was determined via agglutination of reagent A1 and B cells, IgA and IgG were quantified using the Euroimmun anti‐SARS‐CoV‐2 ELISA, and nAb titres were quantified using a microneutralization assay. Differences in titre distribution were examined by ABO blood group using non‐parametric Kruskal–Wallis tests. Adjusted prevalence ratios (aPR) of high nAb titre (≥1:160) were estimated by blood group using multivariable modified Poisson regression models that adjusted for age, sex, hospitalization status and time since SARS‐CoV‐2 diagnosis.ResultsOf the 202 potential donors, 65 (32%) were blood group A, 39 (19%) were group B, 13 (6%) were group AB, and 85 (42%) were group O. Distribution of nAb titres significantly differed by ABO blood group, whereas there were no significant differences in anti‐spike IgA or anti‐spike IgG titres by ABO blood group. There were significantly more individuals with high nAb titre (≥1:160) among those with blood group B, compared with group O (aPR = 1·9 [95%CI = 1·1–3·3], P = 0·029). Fewer individuals had a high nAb titre among those with blood group A, compared with group B (aPR = 0·6 [95%CI = 0·4‐1·0], P = 0·053).ConclusionEligible CCP donors with blood group B may have relatively higher neutralizing antibody titres. Additional studies evaluating ABO blood groups and antibody titres that incorporate COVID‐19 severity are needed.