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A gap exists between in vivo and ex vivo coagulation when investigated by use of the coagulation tests prothrombin time (PT) and activated partial thromboplastin time (APTT). The thrombin generation assay (TGA) has been developed to fill this gap. TGA evaluates thrombin generation (resulting from the action of the procoagulant driver) and decay (resulting from the action of the anticoagulant driver), thus assessing the balance between the two. Coagulation of the test plasma (platelet poor or platelet rich) is activated by small amounts of tissue factor and phospholipids, and the reaction of thrombin generation is continuously monitored by means of a thrombin-specific fluorogenic substrate. Among the parameters derived from the thrombin-generation curve, the most important is the endogenous thrombin potential, defined as the net amount of thrombin that test plasmas can generate on the basis of the relative strength of the pro- and anticoagulant drivers. TGA is therefore the candidate assay to investigate hypo- or hypercoagulability. From my analysis of the literature, I draw the following conclusions. There is strong evidence that TGA is helpful to elucidate coagulation mechanisms in various clinical conditions that until recently were poorly understood (chronic liver disease; diabetes; inflammatory bowel disease, myeloproliferative neoplasms, nonalcoholic fatty liver disease). TGA is a promising laboratory tool for investigating hemorrhagic coagulopathies and monitoring replacement therapy in hemophiliacs, predicting the risk of recurrent venous thromboembolism after a first event, and monitoring patients on parenteral or oral anticoagulants. These applications require clinical trials in which TGA results are combined with specific clinical end points.

D-dimer is a reliable and sensitive index of fibrin deposition and stabilization. As such, its presence in plasma should be indicative of thrombus formation. There are many conditions unrelated to thrombosis in which D-dimer concentrations are high, however, making its positive predictive value rather poor. Notwithstanding these limitations, D-dimer can be regarded as a most valuable laboratory tool to diagnose and manage a vast array of thrombosis-related clinical conditions, including (a) diagnosis of venous thromboembolism (VTE), (b) identification of individuals at increased risk of first thrombotic event (both arterial and venous), (c) identification of individuals at increased risk of recurrent VTE, (d) establishment of the optimal duration of secondary prophylaxis after a first episode of VTE, (e) pregnancy monitoring, and (f) diagnosis/monitoring of disseminated intravascular coagulation (DIC). This article is aimed at reviewing the merits and pitfalls of these applications. From my analysis of the literature, I draw the following conclusions. (a) D-dimer, as measured by a sensitive test, can be safely used to exclude VTE in symptomatic outpatients, provided that it is used in combination with the pretest clinical probability. (b) High concentrations of D-dimer are associated with an increased risk of recurrent VTE. (c) Patients who present with D-dimer above cutoff after stopping the regular course of oral anticoagulation benefit from extended prophylaxis. (d) Finally, D-dimer can be used as a fibrin-related degradation marker for the diagnosis/management of patients with DIC.

Conventional wisdom is that chronic liver disease is an acquired bleeding disorder. However, the imbalance between procoagulant and anticoagulant activities can also lead to thrombosis. Studies are needed to assess the value of anticoagulants. Chronic liver disease, particularly in the end stage, is characterized by clinical bleeding and decreased levels of most procoagulant factors, with the notable exceptions of factor VIII and von Willebrand factor, which are elevated. 1 Decreased levels of the procoagulants are, however, accompanied by decreases in levels of such naturally occurring anticoagulants as antithrombin and protein C. 1 In physiologic conditions, the coagulation system is balanced by these two opposing drivers (Figure 1), but the mechanistic significance of the parallel decrease of both procoagulants and anticoagulants in patients with chronic liver disease escaped attention for many years. As a consequence, chronic liver . . .

The new oral anticoagulants (NOAs) dabigatran, rivaroxaban, and apixaban have proved effective and safe when used in clinical trials, without a need to adjust the dose in response to laboratory testing. This demonstrated efficacy does not necessarily mean that the laboratory, considered the mainstay for the management of the old anticoagulants, will no longer play a role in treatment with NOAs. Laboratories are involved in the management of anticoagulants in 2 ways. The first, monitoring, implies laboratory testing to assess the drug's effect and to adjust the dosage to maintain anticoagulation within the therapeutic interval. This consideration applies to the old drugs. The second way, measurement, implies laboratory evaluations of drug effect to determine whether patients are under- or over-anticoagulated, information that can be useful for decision-making in special circumstances. The latter applies to NOAs. Measurements of the effect of NOAs are indicated in several situations: (a) patients with adverse events (i.e., thrombotic/hemorrhagic), particularly those who present with overdosage owing to excessive drug intake or decreased clearance; (b) patients undergoing surgical procedures for ensuring that no residual drug remains in the circulation; (c) patients requiring anticoagulation reversal because of life-threatening hemorrhage; (d) patients with renal insufficiency, who are likely to accumulate the drug in the circulation; (e) patients with liver failure, because NOAs are metabolized by the liver; (f) patients taking other drugs that might increase/decrease the effects of NOAs via drug-drug interactions. The choice of tests is based on such characteristics as availability, linearity of the dose-response curve, standardization, and responsiveness to increasing drug dosage. Practitioners need to be aware that NOAs can interfere with the measurement of common hemostasis parameters.

Lupus anticoagulant (LA) is one of the three laboratory parameters (the others being antibodies to either cardiolipin or β2-glycoprotein I) which defines the rare but potentially devastating condition known as antiphospholipid syndrome (APS). Testing for LA is a challenging task for the clinical laboratory because specific tests for its detection are not available. However, proper LA detection is paramount for patients’ management, as its persistent positivity in the presence of (previous or current) thrombotic events, candidate for long term anticoagulation. Guidelines for LA detection have been established and updated over the last two decades. Implementation of these guidelines across laboratories and participation to external quality assessment schemes are required to help standardize the diagnostic procedures and help clinicians for appropriate management of APS. This article aims to review the current state of the art and the challenges that clinical laboratories incur in the detection of LA.

The state of clinical art of the coagulopathy of cirrhosis changed considerably over the last decade. Until 2005, cirrhosis was considered as the epitome of the hemorrhagic coagulopathies and the abnormal hemostasis tests associated with the disease were corrected with infusion of fresh frozen plasma or platelets to minimize the risk of bleeding. Since that time, a great deal of work has been done and there is now a change of paradigm. The prothrombin time once considered as an isolated measure of bleeding risk was rejected, and cirrhosis shifted from a purely hemorrhagic construct to a mixed and thrombosis-prone paradigm. In this article we examine the interesting history of how these conceptual changes came about.

The laboratory diagnosis of antiphospholipid syndrome (APS) requires the measurement of solid-phase antibodies to cardiolipin or β2-Glycoprotein-I and the search for lupus anticoagulant (LA). The diagnosis of patients whilst on anticoagulation is impaired by the difficult interpretation of results, at least for LA, owing to the fact that prolongations of clotting times induced by LA superimpose those induced by anticoagulants. This is a matter of concern as treating physicians very often need to know the APS status of their patients to make a decision on secondary antithrombotic prophylaxis. This article aims to review the effect brought about by anticoagulants on APS diagnosis and discuss the options that can be used to overcome such an effect.

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease, and it is anticipated that it could become even more prevalent in parallel with an increase in the incidence of metabolic diseases closely related to NAFLD, such as obesity, type II diabetes, dyslipidemia, and arterial hypertension. In addition to liver impairment, NAFLD is associated with cardiovascular diseases. Fibrosis, atherosclerosis, and venous thrombosis are basically the pathogenic mechanisms behind these clinical manifestations, and all are plausibly associated with hypercoagulability that may, in turn, develop because of an imbalance of pro- vs. anticoagulants and the presence of such procoagulant molecular species as microvesicles, neutrophil extracellular traps (NETs), and inflammation. The assessment of hypercoagulability by means of thrombin generation is a global procedure that mimics the coagulation process occurring in vivo much better than any other coagulation test, and is considered to be the best candidate laboratory tool for assessing, with a single procedure, the balance of coagulation in NAFLD. In addition to defining the state of hypercoagulability, the assessment of thrombin generation could also be used to investigate, in clinical trials, the best approach (therapeutic and/or lifestyle changes) for minimizing hypercoagulability and, hence, the risk of cardiovascular diseases, progression to atherosclerosis, and liver fibrosis in patients with NAFLD.

START-Register--Survey on anTicoagulated pAtients RegisTer--is an independent, inception-cohort, observational, collaborative database aimed at recording prospectively the clinical history of adult patients starting anticoagulant treatment for any reason and using whatever drug. In this article we present the START-Register and give cross section baseline data focusing on non valvular atrial fibrillation (NVAF). Participants are asked to insert prospectively consecutive patients recorded as electronic file on the web-site of the registry. Required data are: demographic and clinical characteristics of patients, associated risk factors for stroke and bleeding, laboratory routine data, clinical indication for treatment, expected therapeutic range (in cases of treatment with vitamin K antagonists -VKAs). The follow-up is carried out to record: quality of treatment (for patients on VKAs), bleeding complications, thrombotic events, and the onset of any type of associated disease. To date 5252 patients have been enrolled; 97.6% were on VKAs because direct oral anticoagulants (DOAC) have been available in Italy only recently. The median age was 74 years [interquartile range (IQR) 64-80]; males 53.7%. This analysis is focused on the 3209 (61.1%) NVAF patients. Mean CHADS2 score was 2.1 ± 1.1, CHADSVASc score was 3.1 ± 1.3;median age was 76 years (IQR 70-81); 168 patients (5.3%) had severe renal failure [Creatinine clearance (CrCl) <30 ml/min]. Moderate renal failure (CrCl 30-59 ml/min) was found in 1265 patients (39.5%). The analysis of the START-Register data shows that two-third of patients who started chronic anticoagulant treatment had NVAF, one-third of them was > 80 years with high prevalence of renal failure.

Emicizumab is a bi-specific humanized monoclonal antibody mimicking the factor (F) VIII cofactor activity in mediating the activation of FX by FIXa. Recent observations showed that emicizumab when added to pooled normal plasma (PNP), hemophilic plasma or PNP added with unfractionated heparin is able to interfere with coagulation assays. To further explore the mechanisms of assay interference we investigated the effect of emicizumab on global coagulation assays for the PNP added with two direct oral anticoagulants, apixaban or argatroban. Aliquots of PNP were added with purified apixaban or argatroban at a concentration of 500 ng/mL and emicizumab at concentrations ranging from 0 to 100 µg/mL. Plasma samples were then tested for the activated partial thromboplastin time (APTT) and for thrombin generation (the latter for the apixaban plasma only). Emicizumab at a 25–50 µg/mL shortened the APTT of the PNP with or without apixaban or argatroban. The extent of correction was greater for the apixaban or argatroban plasma and amounted to 35% or 42%, respectively. The parameters of thrombin generation (lag-time and time-to-peak) for the PNP supplemented with apixaban were shortened by 30% or 25%, respectively and the endogenous thrombin potential and the peak-thrombin were marginally affected. Emicizumab attenuates in vitro the anticoagulant activity of the PNP induced by apixaban or argatroban as documented by the correction of prolonged APTT and velocity of thrombin generation (i.e., lag-time and time-to-peak). Whether the above effects have any relevance in vivo is unknown.