Prompt diagnostic work-up of suspected heparin-induced thrombocytopenia (HIT) is critical for guiding initial patient management. We assessed the performance of three immunoassays detecting anti-PF4/heparin-antibodies, derived a diagnostic algorithm with a short analytical turnaround-time (TAT) and prospectively validated it. Plasma samples were analysed by Zymutest-HIA-IgG, HemosIL-AcuStar-HIT-IgG and ID-H/PF4-PaGIA in retrospective (n=221) and prospective (n=305) derivation cohorts. We calculated likelihood ratios (LR) of result intervals and cut-off values with 100% negative (NPV) and positive (PPV) predictive value for a positive gold-standard functional assay (HIPA). We established a diagnostic algorithm based on the Bayesian combination of pre-test probability and LR of first- and second-line immunoassays. Cut-offs with 100% PPV for positive HIPA were >3.0 U/ml (HemosIL-AcuStar-HIT-IgG) and titre {greater than or equal to}16 (ID-H/PF4-PaGIA); cut-offs with 100% NPV were <0.13 U/ml and {less than or equal to}1, respectively. During the prospective validation of the derived algorithm (n=687), HemosIL-AcuStar-HIT-IgG was used as unique testing in 566/687 cases (82.4%) (analytical TAT 30 min). In 121/687 unresolved cases (17.6%), ID-H/PF4-PaGIA was used as second-line testing (additional TAT 30 min). The algorithm accurately predicted HIT in 51/687 (7.4%) and excluded it in 604/687 (87.9%) patients, leaving only 20/687 (2.9%) cases unresolved. Additionally, we identified 12/687 (1.7%) positive predictions not confirmed by HIPA: 10 patients with probable HIT despite negative HIPA and two possible false positive algorithm predictions. The combination of pre-test probability with first- and second-line immunoassays for anti-PF4/heparin-antibodies is accurate for ruling in or out HIT in {greater than or equal to}95% of cases within 60 minutes. This diagnostic approach improves initial management of patients with suspected HIT.

In the setting of liver cirrhosis (LC), profound hemostatic changes occur, which affect primary hemostasis, coagulation, and fibrinolysis. They involve prohemorrhagic and prothrombotic alterations at each of these steps. Patients with cirrhosis exhibit multifactorial thrombocytopenia and in vitro thrombocytopathy, counterbalanced by increased von Willebrand factor. The resultant shift is difficult to assess, but overall these changes probably result in a rebalanced primary hemostasis. Concerning coagulation, the reduced activity of coagulation factors is counterbalanced by an increase in factor VIII (produced by liver sinusoidal endothelial cells), a decrease of the natural anticoagulants, and complex changes, including changes in circulating microparticles, cell-free DNA, and neutrophil extracellular traps. Overall, these alterations result in a procoagulant state. As for fibrinolysis, increased tissue-type and urokinase-type plasminogen activators, a relatively decreased plasminogen activator inhibitor 1, and decreased levels of thrombin-activatable fibrinolysis inhibitor and α2-antiplasmin are counterbalanced by decreased plasminogen and a decreased fibrin clot permeability. Whether and how these changes shift fibrinolysis remains to be determined. Overall, the current consensus is that in patients with cirrhosis, the hemostasis is shifted toward a procoagulant state. We review the published evidence for the concept of LC as a prothrombotic state, discuss discordant data, and highlight the impact of the underlying cause of LC on the resultant imbalance. (Hepatology 2020;71:2135-2148). Primary HemostasisChanges of primary hemostasis in patients with LC are shown in Table 1.Abbreviations: ADAMTS13, a disintegrin and metalloprotease with thrombospondin type 1 repeats 13;Hepatology, June 2020 ZERMATTEN ET AL. 2136pRoHeMoRRHagIC CHaNgeS thrombocytopenia Thrombocytopenia (platelets <150 × 10 9 /L) occurs in up to 78% (1) of patients with LC, moderate thrombocytopenia (platelets 50-75 × 10 9 /L) occurs in approximately 13%, (2) and severe thrombocytopenia (platelets <50 × 10 9 /L) occurs in 1% to 2%. (3) Decreased production and increased clearance of platelets are both involved in LC-associated thrombocytopenia ( Fig. 1). Indeed, reticulated/immature platelets and glycocalicin (proteolytic extracellular fragment of glycoprotein 1b), which are markers of platelet production, are decreased in LC. (4) However, reticulated/ immature platelet fraction and glycocalicin index, which are markers of platelet turnover, are increased in patients with LC versus healthy donors (4,5) and in thrombocytopenic versus non-thrombocytopenic patients with LC. (4,6) Moreover, the mean platelet survival is decreased in LC, (7) indicating an increased platelet turnover. Differences across LC causes are possible. Indeed, reticulated platelets are increased in hepatitis C virus (HCV)-induced LC and decreased in alcohol-induced LC and hepatitis B virus (HBV)induced LC. (5) DeCReaSeD pRoDUCtIoN oF plateletSDecreased production is due to decre...

Knowledge on heparin-induced thrombocytopenia keeps increasing. Recent progress on diagnosis and management as well as several discoveries concerning its pathogenesis have been made. However, many aspects of heparin-induced thrombocytopenia remain partly unknown, and exact application of these new insights still need to be addressed. This article reviews the main new concepts in pathogenesis, diagnosis, and management of heparin-induced thrombocytopenia.

Procoagulant collagen-and-thrombin (COAT)-activated platelets represent a subpopulation of activated platelets, which retain a coat of prohemostatic proteins and express phosphatidylserine on their surface. Dichotomous intracellular signaling generating procoagulant platelet activity instead of traditional aggregating endpoints is still not fully elucidated. It has been demonstrated that secondary messengers such as calcium and sodium play a critical role in platelet activation. Therefore, we developed a flow cytometric analysis to investigate intracellular ion fluxes simultaneously during generation of aggregating and procoagulant platelets. Human platelets were activated by convulxin-plus-thrombin. Cytosolic calcium, sodium, and potassium ion fluxes were visualized by specific ion probes and analyzed by flow cytometry. We observed high and prolonged intracellular calcium concentration, transient sodium increase, and fast potassium efflux in COAT platelets, whereas aggregating non-COAT platelets rapidly decreased their calcium content, maintaining higher cytosolic sodium, and experiencing lower and slower potassium depletion. Considering these antithetical patterns, we investigated the role of the sodium–calcium exchanger (NCX) during convulxin-plus-thrombin activation. NCX inhibitors, CBDMB and ORM-10103, dose-dependently reduced the global calcium mobilization induced by convulxin-plus-thrombin activation and dose-dependently prevented formation of procoagulant COAT platelets. Our data demonstrate that both NCX modes are used after convulxin-plus-thrombin-induced platelet activation. Non-COAT platelets use forward-mode NCX, thus pumping calcium out and moving sodium in, while COAT platelets rely on reverse NCX function, which pumps additional calcium into the cytosol, by extruding sodium. In conclusion, we described for the first time the critical and dichotomous role of NCX function during convulxin-plus-thrombin-induced platelet activation.

Platelets are active key players in haemostasis. Qualitative platelet dysfunctions result in thrombocytopathies variously characterized by defects of their adhesive and procoagulant activation endpoints. In this review, we summarize the traditional platelet defects in adhesion, secretion, and aggregation. In addition, we review the current knowledge about procoagulant platelets, focusing on their role in bleeding or thrombotic pathologies and their pharmaceutical modulation. Procoagulant activity is an important feature of platelet activation, which should be specifically evaluated during the investigation of a suspected thrombocytopathy.