Review
Author: Chareyre, Corinne ; Camera, Marina ; de Menezes, Erika Marques ; Featherby, Sophie ; Nybo, Jette ; Franco, Corentin ; Burrello, Jacopo ; Brambilla, Marta ; Aharon, Anat ; Kristensen, Soren Risom ; Wahlund, Casper ; Hisada, Yohei ; Orbe, Josune ; Langer, Florian ; Hogwood, John ; Badimon, Lina ; Lacroix, Romaric ; Lucien, Fabrice ; Suades, Rosa ; Bouriche, Tarik ; Snir, Omri ; Hau, Chi ; Beckmann, Lennart ; Bonifay, Amandine ; Roncal, Carmen ; Bolis, Sara ; Martinod, Kimberly ; Campello, Elena ; Gray, Elaine ; Paramo, Jose A ; Norris, Philip ; Benedikter, Birke ; Mullier, François ; Abdili, Evelyne ; Samadi, Nazanin ; Baudar, Justine ; Radu, Claudia M ; Nieuwland, Rienk ; Judicone, Coralie ; Dignat-George, Françoise ; Kim, Yohan ; Sachetto, Ana Teresa Azevedo ; Thaler, Johannes ; Faille, Dorothée ; Latysheva, Nadezhda ; Osterud, Bjarne ; Mackman, Nigel ; Laakmann, Katrin ; Barile, Lucio ; Ettelaie, Camille ; Guldenpfennig, Maite ; Hansen, John-Bjarne
BACKGROUNDScientific and clinical interest in extracellular vesicles (EVs) is growing. EVs that expose tissue factor (TF) bind factor VII/VIIa and can trigger coagulation. Highly procoagulant TF-exposing EVs are detectable in the circulation in various diseases, such as sepsis, COVID-19, or cancer. Many in-house and commercially available assays have been developed to measure EV-TF activity and antigen, but only a few studies have compared some of these assays.OBJECTIVESThe International Society on Thrombosis and Haemostasis Scientific and Standardization Committee Subcommittee on Vascular Biology initiated a multicenter study to compare the sensitivity, specificity, and reproducibility of these assays.METHODSPlatelet-depleted plasma samples were prepared from blood of healthy donors. The plasma samples were spiked either with EVs from human milk or EVs from TF-positive and TF-negative cell lines. Plasma was also prepared from whole human blood with or without lipopolysaccharide stimulation. Twenty-one laboratories measured EV-TF activity and antigen in the prepared samples using their own assays representing 18 functional and 9 antigenic assays.RESULTSThere was a large variability in the absolute values for the different EV-TF activity and antigen assays. Activity assays had higher specificity and sensitivity compared with antigen assays. In addition, there was a large intra-assay and interassay variability. Functional assays that used a blocking anti-TF antibody or immunocapture were the most specific and sensitive. Activity assays that used immunocapture had a lower coefficient of variation compared with assays that isolated EVs by high-speed centrifugation.CONCLUSIONBased on this multicenter study, we recommend measuring EV-TF using a functional assay in the presence of an anti-TF antibody.