Using an age and fibrinogen levels adjusted D-dimer cutoff significantly improves the specificity of two equivalent D-dimer assays for excluding pulmonary embolism.

OBJECTIVES: Our single-center prospective study compared two methods of D-dimer determination used in the exclusion of pulmonary embolism: bioMérieux method, VIDAS® D-Dimer Exclusion™ II, and Diagnostica Stago method, STA®-Liatest® D-Di Plus. For each of these two methods, we calculated optimized variable cutoffs based on fibrinogen and/or age to improve the specificity of the methods. PATIENTS - METHODS: 2530 patients admitted to the Emergency Department of the Brest University Hospital for suspected pulmonary embolism were included in this study. The comparison of the two methods was performed by calculating their different characteristics: sensitivity, specificity and negative predictive value for different cutoffs systems: fixed or age-adjusted according to Douma et al. An optimization of the variable cutoff according to age and fibrinogen was then performed. RESULTS: The two methods VIDAS and STAGO are approximately equivalent in terms of performance even if the STAGO method presents a better specificity (57.1 %) at the fixed cutoff of 0.5 µg/mL. The adoption of age-adjusted, fibrinogen-adjusted or doubly-adjusted (age and fibrinogen) cutoffs, significantly improves the specificity of the tests without affecting their excellent sensitivity. These specificities peak respectively at 75.8 % and 76 % for the VIDAS and STAGO tests when using a doubly-adjusted, age and fibrinogen, cutoff, i.e. a gain in specificity of approximately 10 % compared with the age-adjusted cutoff of Douma et al. and of approximately 20 % compared with the fixed cutoff of 0.5 µg/mL. CONCLUSION: Adopting an optimized variable cutoff based on fibrinogen and/or age significantly improves specificity of D-dimer methods for pulmonary embolism exclusion.

Apport du dosage des monomères de fibrine en situations obstétricales aiguës.

Depuis 2013, nous utilisons le dosage des monomères de fibrine au laboratoire d'hématologie du CHU de Brest. Ce marqueur précoce de l'activation de la coagulation nous permet de détecter très tôt une coagulation intravasculaire disséminée (CIVD) et de suivre son évolution grâce à l'utilisation du rapport monomères de fibrine/D-dimères. Le dosage des monomères de fibrine est utile dans plusieurs contextes cliniques et il est complémentaire de celui des D-dimères. Au travers de deux cas clinico-biologiques, nous allons montrer l'intérêt de ces paramètres dans deux situations obstétricales aigues. Le premier cas clinique traite d'une hémorragie du post-partum compliquée d'une coagulation intravasculaire disséminée. Dans ce cas, les monomères de fibrine ont permis de détecter rapidement l'activation de la coagulation. Le deuxième cas clinique traite d'une prise en charge d'un placenta percreta compliqué d'une coagulation intravasculaire disséminée, pour lequel les monomères ont aidé à la prise en charge chirurgicale.

New considerations on pathways involved in acute traumatic coagulopathy: the thrombin generation paradox.

Background: An acute traumatic coagulopathy (ATC) is observed in about one third of severely traumatized patients. This early, specific, and endogenous disorder is triggered by the association of trauma and hemorrhage. The early phase of this condition is characterized by the expression of a bleeding phenotype leading to hemorrhagic shock and the late phase by a prothrombotic profile leading to multiple organ failure. The physiopathology of this phenomenon is still poorly understood. Hypotheses of disseminated intravascular coagulation, activated protein C-mediated fibrinolysis, fibrinogen consumption, and platelet functional impairment were developed by previous authors and continue to be debated. The objective of this study was to observe general hemostasis disorders in case of ATC to confront these hypotheses. Method: Four groups of 15 rats were compared: C, control; T, trauma; H, hemorrhage; and TH, trauma and hemorrhage. Blood samples were drawn at baseline and 90 min. Thrombin generation tests, platelet aggregometry, and standard hemostasis tests were performed. Results: Significant differences were observed between the baseline and TH groups for aPTT (17.9 ± 0.8 s vs 24.3 ± 1.4 s, p < 0.001, mean ± SEM), MAP (79.7 ± 1.3 mmHg vs 43.8 ± 1.3 mmHg, p < 0.001, mean ± SEM), and hemoglobin (16.5 ± 0.1 g/dL vs 14.1 ± 0.3 g/dL, p < 0.001, mean ± SEM), indicating the presence of an hemorrhagic shock due to ATC. Compared to all other groups, coagulation factor activities were decreased in the TH group, but endogenous thrombin potential was (paradoxically) higher than in group C (312 ± 17 nM/min vs. 228 ± 23 nM/min; p = 0.016; mean ± SEM). We also observed a subtle decrease in platelet count and function in case of ATC and retrieved an inversed linear relationship between fibrinogen concentration and aPTT (intercept, 26.53 ± 3.16; coefficient, - 3.40 ± 1.26; adjusted R2: 0.1878; p = 0.0123). Conclusions: The clinical-biological profile that we observed, combining normal thrombin generation, fibrinogen depletion, and a hemorrhagic phenotype, reinforced the hypothesis of activated protein C mediated-fibrinolysis. The key role of fibrinogen, but not of the platelets, was confirmed in this study. The paradoxical preservation of thrombin generation suggests a protective mechanism mediated by rhabdomyolysis in case of major trauma. Based on these results, we propose a new conception concerning the pathophysiology of ATC.

A very potent factor V inhibitor interferes with the levels of all coagulation factors and causes a fatal hemorrhagic syndrome.

We report a very high factor V inhibitor affecting the measurement of all coagulation factors besides fibrinogen, all these factors being dramatically decreased. This inhibitor could be linked to antibiotic use. The patient died of massive hemorrhage before a plasma exchange could be initiated.

Comparison of four methods to assess high-on platelet reactivity under P2Y12 receptor inhibitor.

P2Y12 receptor inhibitors are antiplatelet agents commonly prescribed in the treatment of coronary artery disease. Their efficacy can be limited by high on-treatment platelet reactivity (HPR), which can be evaluated by different biological assays. Most commonly, HPR is evaluated by flow cytometric vasodilator-stimulated phosphoprotein-phosphorylation (VASP-P) assay, which can be time consuming. To evaluate the potential interest of novel technologies, we compared four different assays. Ninety patients receiving P2Y12 inhibitors were included. Four technologies were evaluated: the current standard test measuring VASP-P by flow cytometry, the historical reference test based on light transmittance aggregation (LTA), and two relatively novel techniques: whole blood multiple electrode aggregometry (MEA) and platelet function analyzer (PFA), which are less time consuming. The three latter tests were compared with the VASP-P assay as a reference using receiver operating characteristics (ROC) analysis: LTA has an excellent comparability with the VASP test (ROC AUC > 0.9); the other two tests (multiplate and PFA) have only satisfactory comparability (ROC AUC around 0.7) and therefore may not replace the VASP "gold standard" test, if importance is attached to a quantitative assessment of the substitution parameter of VASP. Nevertheless, if a binary approach of the anti-aggregation result is sought, then one can conclude that the three tests are equivalent since Cohen's kappa coefficients are very close for the three tests (k = 0.548 for LTA; k = 0.554 for MEA; k = 0.570 for PFA/P2Y), and a similar proportion of patients are misclassified (15% for LTA, 14% for MEA, and 13.6% for PFA). Discriminant factor analysis using all the parameters provided by each test did not improve the diagnostic performance of MEA or PFA. In conclusion, only LTA shows a good comparability to the VASP assay using ROC curve analysis, probably because misclassified patients have results close to the cutoff values. All three tests have moderate agreement regarding the classification of patients as responders to P2Y12 inhibition.

Risk factors for recurrent venous thromboembolism after unprovoked pulmonary embolism: the PADIS-PE randomised trial.

We aimed to identify risk factors for recurrent venous thromboembolism (VTE) after unprovoked pulmonary embolism.Analyses were based on the double-blind randomised PADIS-PE trial, which included 371 patients with a first unprovoked pulmonary embolism initially treated during 6 months who were randomised to receive an additional 18 months of warfarin or placebo and followed up for 2 years after study treatment discontinuation. All patients had ventilation/perfusion lung scan at inclusion (i.e. at 6 months of anticoagulation).During a median follow-up of 41 months, recurrent VTE occurred in 67 out of 371 patients (6.8 events per 100 person-years). In main multivariate analysis, the hazard ratio for recurrence was 3.65 (95% CI 1.33-9.99) for age 50-65 years, 4.70 (95% CI 1.78-12.40) for age >65 years, 2.06 (95% CI 1.14-3.72) for patients with pulmonary vascular obstruction index (PVOI) ≥5% at 6 months and 2.38 (95% CI 1.15-4.89) for patients with antiphospholipid antibodies. When considering that PVOI at 6 months would not be available in practice, PVOI ≥40% at pulmonary embolism diagnosis (present in 40% of patients) was also associated with a 2-fold increased risk of recurrence.After a first unprovoked pulmonary embolism, age, PVOI at pulmonary embolism diagnosis or after 6 months of anticoagulation and antiphospholipid antibodies were found to be independent predictors for recurrence.

Decreased turnover aspirin resistance by bidaily aspirin intake and efficient cytoreduction in myeloproliferative neoplasms.

Essential thrombocythemia (ET) and polycythemia vera (PV) are myeloproliferative neoplasms (MPN) with an increased risk of arterial and venous thrombosis. Aspirin is recommended to reduce this risk, but resistance to antiplatelet therapy seems to hamper its efficacy in some patients. We have previously shown that multiple electrode aggregometry (MEA) was a valuable tool to assess aspirin resistance in MPN. In this study, MEA was used to assess the reduction in aspirin resistance after bi-daily (BID) aspirin intake or cytoreduction. Fifty one MPN patients (31 ET and 20 PV) receiving 75 mg aspirin once daily (OD) or BID, with or without cytoreductive treatment, were analyzed. Aspirin resistance was assessed using whole blood MEA (Multiplate®, Roche Diagnostics, Meylan, France). In all patients, global aspirin resistance consisted mainly of turnover resistance (TOR). 94% of patients with OD aspirin intake and without cytoreduction displayed biological aspirin resistance. By switching to a BID aspirin regimen, the proportion of resistant patients reduced to 47%. Cytoreduction also contributed to reduce aspirin resistance in a similar way (50% of aspirin resistant patients). Combining cytoreduction and BID aspirin regimen was the most efficient way to reduce aspirin resistance yielding to 12% resistant patients. Moreover, a nonlinear correlation was observed between TOR and naive platelet counts regardless of aspirin regimen. Last, mutational status did not seem to affect TOR. This study confirmed that BID aspirin is biologically more effective than OD aspirin in reduction of aspirin resistance. The latter was achieved through a reduction in TOR which was also decreased by cytoreductive therapy.

Thrombin Generation Measurements in Patients Scheduled for Laparoscopic Bariatric Surgery.

PURPOSE: Obese patients are known to be in an in vitro hypercoagulable state relative to normal-weight patients. Our study aimed to identify markers of enhanced coagulability (endogenous thrombin potential (ETP)) in morbidly obese patients using the thrombin generation (TG) test. MATERIALS AND METHODS: All patients scheduled for laparoscopic bariatric surgery (LBS) between September 1, 2014 and January 31, 2016 were eligible for our prospective study. We used logistic regression to compute the odds ratio (OR) across ETP quartile distributions to evaluate the risk of enhanced TG. RESULTS: We studied 102 patients, 77.5% were female, mean age was 41.2 ± 12.1 years, and mean BMI was 45.5 ± 7.0 k/m2. Total cholesterol and fibrinogen levels were found to be independent risk factors for patients in the 4th quartile distribution of the ETP distribution (OR (95% CI)) 2.6 (1.2 to 5.4) (P = 0.01) and 2.2 (1.1 to 4.5 (P = 0.03). Patients in the 4th quartile of the ETP distribution had a lower ETP 1 month after surgery (157 (144-196) vs. 120 (98-140); P < 0.001) in parallel with a trend toward lower total cholesterol levels (5.0 ± 0.9 vs. 4.4 ± 1.0; P = 0.06). Fibrinogen levels were stable (4.5 ± 1.0 vs. 4.4 ± 0.9); P = 0.7). CONCLUSIONS: Our study highlights the role of total cholesterol and blood inflammatory marker levels in enhancing ETP in morbidly obese patients. Further studies are necessary to confirm the decreased ETP following LBS with the expected reduced inflammatory marker and total cholesterol levels.

Reduction of coagulability state one year after bariatric surgery.

BACKGROUND: Obese patients are in a hypercoagulable state relative to normal-weight patients. Low-grade inflammation may be a key factor for this condition. OBJECTIVES: Our study aimed to compare the coagulability state of morbidly obese patients before and 1 year after bariatric surgery (BS) using the Thrombin Generation (TG) test, a validated method to assess coagulation in vitro. SETTING: University hospital. METHODS: All patients undergoing BS between September 1, 2014 and April 30, 2015 were eligible for this prospective study (n = 42). Two distinct reagents were used for TG initiation based on the tissue factor concentration (Reagents LOW and HIGH). The main outcomes were endogenous thrombin potential (ETP) and peak height of TG. The rate of follow-up after one year was 97%. RESULTS: One year after surgery, %weight loss was 32.5±8.4%; CRP decreased from 9.0 (3.7-12.9) to 1.1 (0.3-2.8) mg/mL (P<.001) and fibrinogen from 4.2±.8 to 3.5±.8 g/L (P<.001). The ETP (%) decreased from (108.0 (95.0-117.0) to 78.0 (71.0-98.0) (P<.001) (LOW reagent) and from 113.0 (103.0-134.0) to 96.0 (86.0-107.0) (P<.001) (HIGH reagent). Peak height (%) decreased from (117.0 (92.0-139.0) to 82.0 (70.0-111.0) (P = .003) (LOW reagent) and from 106.0 (96.0-118.0) to 97.0 (87.8-105.2) (P = .003) (HIGH reagent). CONCLUSION: Our study shows a significant reduction in TG potential one year after BS in morbidly obese patients. Reduction of low grade inflammation may be one of the underlying mechanisms.

Multiple Electrode Aggregometry is an adequate method for aspirin response testing in myeloproliferative neoplasms and differentiates the mechanisms of aspirin resistance.

INTRODUCTION: In myeloproliferative neoplasms (MPN), aspirin reduces the thrombotic risk. Nevertheless, aspirin resistance may be due to excessive platelet production ("turnover" resistance). Aspirin resistance can also result from a lack of effect of aspirin; this second component is called "intrinsic resistance". Two biological tests are considered reference methods for the assessment of aspirin resistance: TXB2 assay and Light Transmittance Aggregometry (LTA) with arachidonic acid. MATERIALS & METHODS: We have compared a third method, the Multiple Electrode Aggregometry (MEA), performed with arachidonic acid on the Multiplate® analyzer, with both reference methods. Thirty-six patients with MPN were assessed for aspirin resistance with all three techniques. 30 patients devoid of MPN were used as controls. RESULTS: The three methods were statistically equivalent: LTA and TXB2 were comparable methods (ROC curve AUC=0.844>0.7; LTA cutoff=67%). At this threshold, LTA had a sensitivity of 73% and a specificity of 96%. MEA (without added aspirin) and TXB2 were also comparable (ROC curve AUC=0.782; MEA cutoff=31U), but at this threshold, 11 patients (30%) were falsely positive with MEA. Last, MEA and LTA were comparable (ROC curve AUC=0.888; MEA cutoff=56U), with a sensitivity of 90% and a specificity of 84.6%. Besides, MEA gave an insight into the mechanism of aspirin resistance (turnover and/or intrinsic). CONCLUSION: MEA is both rapid and reliable as compared to reference methods. Clinical correlation with risk of re-thrombosis should definitively validate this method and the best cutoff value.