Seminars in thrombosis and hemostasis最新文献

Platelets play a central role in primary hemostasis and arterial thrombosis, and accumulating evidence suggests that physical exercise can modulate platelet function. Acute vigorous or exhaustive bouts commonly produce transient thrombocytosis, enhanced aggregation and degranulation (e.g., P-selectin, β-TG, and PF4), increased thromboxane generation, and short-lived shifts toward hypercoagulability; these responses seem to scale with exercise intensity, adrenergic drive, and shear stress and may be amplified in untrained or high-risk individuals. By contrast, repeated training across modalities (aerobic, resistance, and high-intensity interval) generally lowers resting platelet reactivity, augments endothelial nitric oxide (NO) bioavailability, improves redox balance, and strengthens fibrinolytic capacity. These favorable adaptations may diminish with detraining, suggesting that the platelet-modulating effects of exercise are dynamic and contingent on consistent training exposure. In this review, we examine the association between platelet function and distinct exercise modalities, including aerobic, resistance, and high-intensity training, influence. We compare exercise modalities, intensities, and fitness states and consider major methodological sources of heterogeneity (assay selection, sampling timing, exercise prescription, and inter-individual variability) that complicate interpretation. Clinically, regularly performed, appropriately progressed exercise appears net favorable for hemostatic balance, whereas unaccustomed extreme exertion in high-risk individuals should be approached with preparation and caution. Better-standardized protocols and biomarker-informed trials are needed to refine exercise prescriptions for reducing thrombotic risk.

Autoimmune acquired coagulation factor deficiency (AiCFD) represents a rare coagulation disorder that primarily affects older people and sometimes causes fatal bleeding; therefore, clinicians need to consider this when encountering patients with unexplained bleeding. AiCFD is caused by the production of autoantibodies against one's own coagulation factor, which markedly inhibit its function, or accelerate its clearance from plasma, resulting in hemostatic failure. The plasma of affected patients shows various abnormal findings, because anti-coagulation factor autoantibodies are polyclonal, and each clone has different properties. First, inhibitor type autoantibodies target the functional sites of coagulation factors, thereby considerably reducing their activity. Second, clearance-accelerating autoantibodies bind to non-functional sites and cause rapid removal of coagulation factors from the blood, thereby reducing their levels (and their activity in parallel). Third, mixed type autoantibodies (inhibitory clearance-accelerating) substantially reduce coagulation factor activity and level to various degrees. Most anti-coagulation factor autoantibodies are inhibitory clearance-accelerating types, although pure inhibitor types remain clinically significant; however, the pure clearance-accelerating type appears to be rare, possibly because the autoantibody is not detected unless it exceeds the level of the target coagulation factor (pseudo-autoantibody negative). Moreover, anti-factor XIII autoantibodies are particularly complex, as they interfere with the A subunit (Aa type), its activated form (Ab type), and/or the B subunit (B type). Of the three types, Aa type anti-factor XIII autoantibodies contain a mixture of different inhibitor type autoantibodies in various ratios in plasma, resulting in an extremely diverse range of test findings. Therefore, care must be taken when diagnosing and assessing the efficacy of treatment.

Antiphospholipid syndrome (APS) diagnosis hinges on identifying antiphospholipid antibodies (aPL). Currently, laboratory testing encompasses lupus anticoagulant (LA), anticardiolipin (aCL), and anti-β2-glycoprotein I antibodies (aβ2GPI) IgG or IgM, which are included in the APS classification criteria. All the assays needed to detect aPL antibodies have methodological concerns. LA testing remains challenging due to its complexity and susceptibility to interference from anticoagulant therapy. Solid phase assays for aCL and aβ2GPI exhibit discrepancies between different assays. Antibody profiles aid in identifying the patients at risk for thrombosis through integrated interpretation of all positive aPL tests. Antibodies targeting domain I of β2-glycoprotein and antiphosphatidylserine-prothrombin antibodies have been evaluated for their role in thrombotic APS but are not yet included in the APS criteria. Detecting these antibodies may help patients with incomplete antibody profiles and stratify the risk of APS patients. The added diagnostic value of other methodologies and measurements of other APS-associated antibodies are inconsistent. This manuscript describes laboratory parameters useful in the diagnosis of thrombotic APS and will concentrate on the laboratory aspects, clinical significance of assays, and interpretation of aPL results in the diagnosis of thrombotic APS.

Factor VIII (FVIII) inhibitors represent antibodies that develop against coagulation FVIII and reduce FVIII functional activity. FVIII inhibitors may develop in patients with congenital hemophilia A (CHA) in response to infused FVIII (allo-antibodies) or in patients without CHA in a variety of situations (auto-antibodies; acquired hemophilia A). We report updated findings for FVIII inhibitor testing in our geographic region using recent data (testing for the past 5 years; 2020-2024 inclusive) from the RCPAQAP (Royal College of Pathologists of Australasia Quality Assurance Program), an international external quality assessment (EQA) program, with over 80 enrolments for the FVIII inhibitor module. Four samples are assessed each year, with these comprising both FVIII inhibitor negative samples and FVIII inhibitor positive samples with various inhibitor titers. This EQA data largely evidences favorable findings in FVIII inhibitor testing in our jurisdiction, with >99% of test results interpreted correctly by participants for the presence ("detected") or absence ("not detected") of FVIII inhibitors in assessed samples. Moreover, most errors in interpretation appear to be transcription or data entry errors rather than analytic errors. The coefficient of variation (CV) values for FVIII inhibitor samples were moderately high, ranging from 25 to 40%, irrespective of the inhibitor titer (range: 3-64 Bethesda units [BU]/mL) or the method (i.e., Bethesda vs. Nijmegen). In conclusion, most laboratories were able to correctly identify the presence versus absence of FVIII inhibitors, although laboratory-reported titers varied moderately.

D-dimer assessment has several established roles in venous thromboembolism (VTE) and disseminated intravascular coagulation diagnosis, and recently the risk stratification of coronavirus disease 2019 (COVID-19). D-dimer assays are neither standardized nor harmonized, use varying methodologies, and use different reporting units, all resulting in a lack of interchangeability and generalizability of assays. Using large multiyear datasets from an international laboratory quality assurance program, we assessed (1) common D-dimer assays in use worldwide, (2) differences in analytical performance between different methods, and (3) interlaboratory variability between positive samples. External proficiency testing results from laboratories participating in the External Quality Control for Assays and Tests (ECAT) Foundation were analyzed from 2017 to 2023. Annually, between 578 and 690 laboratories participated in the D-dimer sample surveys with response rates ranging from 88 to 97%. The three most common assays in use in 2023 were the Siemens Innovance D-dimer (42%), the IL HemosIL D-dimer HS 500 (20%), and the Diagnostica Stago (Stago) Liatest D-dimer Plus (10%)-all these are automated, quantitative, latex immunoassays expressed in fibrinogen equivalent units (FEU). The highest interlaboratory variability was observed around the typical VTE exclusion threshold of 0.5 mg/L FEU. Lower interlaboratory variability was observed at values above 0.8 mg/L FEU. Our study provides recent, international performance data on currently used D-dimer assays and describes the significant variability between assays and across D-dimer concentrations. We demonstrate that assays are not interchangeable and that using them interchangeably has the potential to result in clinically important errors. There is an urgent need to educate users about these issues and to work towards harmonizing D-dimer units and reporting.

The activated partial thromboplastin time (aPTT) and anti-factor-Xa levels (anti-Xa) are both used to monitor patients on unfractionated heparin. Our previous study demonstrated that patients with discordant high aPTT relative to anti-Xa had higher rates of mortality and bleeding events.To determine if underlying patient characteristics drive both discordance and adverse outcomes or if discordance is an independent risk factor to adverse outcomes.We analyzed all patients hospitalized at the Stanford Hospital between January 2011 and December 2019 who had simultaneous aPTT and anti-Xa levels performed. From the electronic medical record, we extracted and analyzed 51 patient features including baseline coagulation laboratory results, demographics, values of other common laboratories (basic metabolic panel, complete blood count, etc.), diagnostic procedures, medications, and death.A total of 17,728 patients had 78,701 paired aPTT and anti-Xa levels. Patients with discordant aPTT and anti-Xa where aPTT (seconds) was elevated beyond the expected therapeutic range had a higher 30-day mortality (odds ratio [OR]: 2.16, 95% confidence interval [CI]: 1.78-2.63, p < 0.001). Sectioning the patients based on the degree of discordance and whether aPTT or anti-Xa were signaling excess anticoagulation, we found those with an elevated aPTT discordant to their anti-Xa level had the highest odds of death (OR: 2.46, 95% CI: 1.99-3.10) compared with the concordant group. This finding was still present after controlling for patient comorbidity and other laboratory results at hospital admission.After controlling for patient features strongly associated with increased mortality in heparinized patients, we identified that the discordant pattern of high aPTT to anti-Xa served as an independent predictor of 30-day all-cause mortality, with a higher degree of discordance associated with increased odds of 30-day mortality.

D-dimers represent the breakdown products of fibrin. Thus, elevated plasma D-dimers will arise following a thrombotic event, such as a deep vein thrombosis or a pulmonary embolism, and therefore, a nonelevated D-dimer is used to effectively exclude such events. D-dimers are also elevated in a range of other conditions, for example, during disseminated intravascular coagulation. D-dimer levels may also be associated with prognostic value. For example, highly raised D-dimer levels can be associated with worsening clinical features in coronavirus disease 2019. Thus, D-dimer testing represents a commonly requested hemostasis test, often performed in 24/7 laboratories. Unfortunately, D-dimer testing is neither standardized nor harmonized across manufacturers or laboratories. Indeed, considering reporting units and the magnitude of units, up to 28 different combinations may be reported by laboratories. We provide updated findings for D-dimer testing in our geographic region, using recent data from the Royal College of Pathologists of Australasia Quality Assurance Programs, an international external quality assessment program, currently with over 450 participants in the D-dimer module. Data show a wide variety of assays in use and variable outcomes in reported numerical values when assessing proficiency samples. D-dimer testing mostly comprised reagents from three main manufacturing suppliers, with a small number of users of reagents from other manufacturers. Reported results showed important differences in numerical values for the same homogeneous tested samples when normalized to a single reporting unit (e.g., mg/L). Nevertheless, despite using different test reagents and reporting, most participants uniformly identified D-dimer values as below or above a "detection" cut-off for samples that were constructed to be below or above most cut-off values. As expected, mixed findings were reported for samples containing levels around expected cut-off values. We hope that our findings, reflecting on the heterogeneity of test reagents and test data, help improve diagnostic testing for D-dimer testing and facilitate harmonization and standardization, in the future.

External quality assessment (EQA) is used to evaluate laboratory performance in tests of hemostasis; however, some esoteric tests are performed by too few centers in any one EQA program to allow valid statistical assessment. To explore the feasibility of pooling data from several EQA providers, an exercise was carried out by the External Quality Assurance in Thrombosis and Haemostasis group, using the International Society on Thrombosis and Haemostasis Scientific and Standardization Committee (SSC) plasma standard for thrombophilia screening assays. Six EQA providers took part in this exercise, distributing the SSC plasma standard as a "blinded" sample to participants for thrombophilia tests between November 2020 and December 2021. Data were collected by each provider, anonymized, and pooled for analysis. Results were analyzed as overall results from each EQA provider, and by kit/method-specific comparisons of data from all providers pooled together. For each parameter, median results and range were determined. Over 1,250 sets of data were returned in the six EQA programs. The overall medians (all data pooled) were <4% of the assigned values for each parameter with the exception of protein C activity by clot-based assay. Method-related differences in median results were observed for free protein S antigen and protein S activity-a pattern seen across data from the different EQA providers. Antithrombin antigen results reported in mg/dL provided an example where small numbers of results for a single EQA provider may be supplemented by pooling data from multiple providers with good agreement seen among results reported by the different EQA providers. This study demonstrated that a multicenter EQA provider collaboration can be carried out and demonstrated benefit for assays with smaller number of participants. In addition, results showed good agreement with the assigned values of the SSC plasma standard. Further exercises for tests performed by only small numbers of laboratories can be planned.

ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13), also called von Willebrand factor (VWF) cleaving protease, acts as a moderator of VWF activity. ADAMTS13 cleaves VWF multimers, thereby reducing VWF activity in blood. When ADAMTS13 is absent (e.g., in patients with TTP [thrombotic thrombocytopenia purpura]), accumulation of VWF in plasma can occur, particularly as "ultra-large" VWF multimers, with this leading to adverse outcomes such as thrombosis. Relative ADAMTS13 deficiencies also occur in several other conditions, including secondary thrombotic microangiopathies (TMA), cancer, and with severe infections such as in COVID-19 (coronavirus disease 2019). These situations might therefore be accompanied with relative loss of ADAMTS13, thereby potentially also leading to pathological VWF accumulation, with this then generating a prothrombotic milieu, thus contributing to enhance the risk of thrombosis. Laboratory testing for ADAMTS13 can aid in the diagnosis of such disorders (i.e., TTP, TMA), and help guide their management, with testing now accomplished using various assays. As most presentations of TTP reflect an acquired condition due to anti-ADAMTS13 antibodies, there may also be a need to test for these, as this will also influence clinical management. We herein provide an overview of TTP, note other conditions in which low levels of ADAMTS13 may be present, and then detail laboratory testing for both ADAMTS13 and associated inhibitors.