Brigitte Tardy-Poncet

Evolution of blood coagulation and fibrinolysis parameters after abrupt versus gradual withdrawal of acenocoumarol in patients with venous thromboembolism: a double‐blind randomized study

A double‐blind randomized trial was conducted to research a hypercoagulable state rebound after abrupt versus gradual withdrawal of acenocoumarol. 20 patients were included: 10 in the abrupt withdrawal group (AW) and 10 in the gradual withdrawal group (GW). Between days 1 and 15, F1+2 was higher in group AW (P<0.002). A sig‐nificant increase of D‐dimer with time was found (P<0.001) without difference between the two groups. tPA and PAI‐1 levels remained stable throughout without difference between the two groups. No rebound phenomenon was observed. Four thrombotic recurrences were observed: group AW: 1, group GW: 3 (P=0.29). There is neither clinical nor biological support for a gradual anticoagulation withdrawal.

EFFECTS OF LONG TRAVELS IN SITTING POSITION IN ELDERLY VOLUNTEERS ON BIOLOGICAL MARKERS OF COAGULATION ACTIVATION AND FIBRINOLYSIS

OBJECTIVE To evaluate whether long travel in sitting position is associated with an increase of coagulation activation and/or a decrease of fibrinolytic activity. DESIGN Comparison of blood coagulation and fibrinolysis parameters before and after two pleasure trips by bus organized in winter period (600 km in 8 hours) and in summer period (1200 km in 16 hours). SUBJECTS 31 and 23 healthy elder volunteers for the winter and the summer trip respectively. Nine other elder volunteers were selected as a control group for the winter study. MAIN OUTCOME MEASURES prothrombin fragment 1 + 2 (F1 + 2), thrombin-antithrombin III (TAT), D-dimers (D-D), factor VII activated, plasminogen activator inhibitor (PAI), tissue-type plasminogen activator (t-PA), plasma albumin. RESULTS A significant difference before and after the travel was only observed for TAT in the summer period. However all values of TAT were in the normal range. No volunteer presented with thromboembolic disease during the month following the travel. CONCLUSION In the condition of our study, long travel in sitting position does not lead to an enhanced procoagulant state for elderly with varicose veins. These results suggest that there is no biological support to propose heparin prophylactic therapy for the elderly with varicose veins wishing to travel by bus.

Heparin-Induced Thrombocytopenia

Heparin therapy may sometimes be seriously complicated by heparin-induced thrombocytopenia (HIT). Heparin use for treatment and prevention of thromboembolism is more common in the elderly and that may be the reason why HIT is reported more frequently in this group of patients. The first approach in the management of HIT is awareness of this disorder. The morbidity and mortality associated with HIT may be reduced by avoiding unnecessary heparin exposure, by reducing the duration of heparinisation and by using low molecular weight heparins rather than unfractionated heparin. A decrease from baseline values of at least 30% in the platelet count, any unexplained thrombotic event and the finding of a white clot at thrombectomy are clinical warning signs that should alert physicians to a possible diagnosis of HIT. Indeed, early clinical recognition of HIT may sometimes prevent the severe complications associated with this disorder. Objective confirmation of the diagnosis of HIT is difficult because none of the available biological tests possess 100% sensitivity or 100% specificity. It is, however, possible to optimise the performances of the functional assay, mainly the platelet aggregation test (PAT), by following the manoeuvres described by different investigators. The use of 2 classes of assay (functional and antigen assays) and repeat testing on another day can avoid misdiagnosis of HIT. An alternative parenteral anticoagulant treatment is most often mandatory after heparin withdrawal. Danaparoid sodium and lepirudin are 2 drugs that are currently available for the treatment of HIT, and the efficacy of argatroban needs to be confirmed in greater numbers of patients with HIT. The use of these drugs has contributed to the reduction in the mortality and morbidity associated with HIT.

Experts' opinion or the serotonin release assay as a gold standard for the diagnosis of heparin-induced thrombocytopenia (HIT)?

Heparin-induced thrombocytopenia (HIT) is a worrisome adverse drug reaction, widely thought to be caused by plateletactivating antibodies reactive against complexes between heparin and chemokines, most often but not always platelet factor 4 (PF4). HIT is challenging to diagnose clinically, as the cardinal clinical features of HIT, thrombocytopenia and thromboembolism in the setting of a proximate heparin exposure, are common findings among hospitalized patients for whom other plausible explanations exist [1]. Two types of assay are available for laboratory detection of HIT antibodies. Immunoassays (IAs) detect the presence of antibodies directed towards PF4–heparin complexes, whereas functional assays aim at detecting heparin-dependent platelet activation induced by these antibodies. While IAs are sensitive for detecting antiPF4–heparin antibodies, although they do not detect antibodies directed against other chemokines than PF4 [2], their major drawback is a poor specificity as many patients exposed to heparin develop anti-PF4–heparin antibodies detectable by IA in the absence of HIT [3]. Platelet activation assays such as the platelet serotonin release assay (SRA) detect heparin-dependent antibodies that can bind to and activate platelets via their Fc gamma receptors. The reported sensitivity and specificity of SRA are up to 100% and 97%, respectively, for UFH– and LMWH-treated patients [4]. Inmany studies regarding patients with a clinical suspicion of HIT, SRA is used as the gold standard for HIT diagnosis. Recently, the diagnosis of HIT was for the first time based on the opinion of three independent experts [5] blinded to the results of both SRA (performed using the method described by Sheridan et al.) and IA. Surprisingly, it is reported in this study that both sensitivity and specificity of SRA were lower (71.4% [29–96.3] and 93% [80.9–98.5], respectively with 95% confidence intervals [CI]). So we looked at what would have been the results of previous studies that used SRA as the gold standard, had these revised SRA sensitivity and specificity values been used. We undertook a systematic review of all published validation studies for 4 Ts scores and IA HIT tests. The Medline database was used to find appropriate studies published during a 5-year period, from 2005 to 2010. Only studies evaluating a clinical score and/or an IA with HIT diagnosis based on SRA as the gold standard were considered. The sensitivity and specificity (95%CI) of the 4 Ts probability score and the IA were then reassessed by incorporating the diagnostic performance of SRA reported by Cuker et al. [4]; referred to as revisited sensitivity and specificity. Five studies evaluating a clinical score (4 Ts) [6–10] and three studies evaluating an IA were included [6,8,10]. In all of these studies but one [9], HIT was diagnosed if serotonin release was > 20% with 0.1 U mL heparin and < 20% with 100 U mL heparin. In one previous study [9], SRA was considered positive when serotonin release was > 50%. The sensitivity and specificity (reported and revisited) associated with high or low 4 Ts scores, of a particle gel immunoassay (H/ PF4 PaGIA ; Diamed SA, Cressier sur Morat, Switzerland) and of two ELISA assays (HAT45 ; GTI, Brookfield, WI, USA and Zymutest HUA IgG/A/M ; Hyphen Biomed, Neuville sur Oise, France) are shown in Table 1. While the revisited specificities associated with high 4 Ts scores were slightly lower than originally reported in most studies, major decreases were observed for the revisited sensitivities associated with both low 4 Ts scores and the various commercial IAs. It follows that the power of a low 4 Ts score and/or a negative IA to rule out HIT appears unacceptably low in clinical practice. What can explain these results and the discrepancy between SRA results and experts opinion? First, SRA quality control has only been described in one previous study [9]. Not using washed platelets from at least two suitable donors, as well as positive HIT control sera, to verify that the platelets are sufficiently reactive, is the most commonly reported inconsistent practice [11] leading to a high risk of false-negative results. Second, it is well known that, in daily practice, SRA results may be borderline, intermediate or non-specific. The rate of such results is not reported in studies but this can explain both false-negative and false-positive results, depending on how results are Correspondence: Bernard Tardy, Université Jean Monnet, Inserm CIE3, CHU Saint Etienne, France. Tel.: +33 4 7712 0797; fax: +33 4 7712 7820. E-mail: bernardtardy@yahoo.fr

Delayed-onset heparin-induced thrombocytopenia without thrombosis in a patient receiving postoperative thromboprophylaxis with rivaroxaban

Delayed-onset heparin-induced thrombocytopenia without thrombosis in a patient receiving postoperative thromboprophylaxis with rivaroxaban -

Extremely low doses of lepirudin in a patient with heparin-induced thrombocytopenia, high bleeding risk and renal insufficiency

Heparin-induced thrombocytopenia is a rare but severe complication of heparin therapy that carries a high risk of thrombosis, a thrombotic complication that occurs in over half the patients affected (Warkentin & Greinacher, 2004). In France, two drugs are available for the treatment of HIT: danaparoid (Magnani, 1997) and lepirudin (Lubenow et al, 2005). Both these drugs are eliminated via the kidneys and their half-lives, normally 25 and 2 h, respectively, are greatly prolonged in patients with renal insufficiency. We report the case of a 55-year-old man with a long history of systemic lupus erythematosus and antiphospholipid syndrome. In view of recurrent venous thrombosis events in the past, he was on long-term oral anticoagulant treatment. He was admitted to an Intensive Care Unit with headache and consciousness disorder. The brain computed tomography (CT) scan revealed a cerebral haematoma. Oral anticoagulant treatment was stopped, without vitamin K reversal. On day 5, the platelet count was 160 · 10/l and the International Normalized Ratio (INR) was 1Æ15. Given the patient’s long history of venous thrombosis, intravenous unfractionated heparin (UFH) was started for venous thrombophylaxis, but 12 h later, the patient developed thrombocytopenia (79 · 10/l). On day 6, UFH was stopped for 38 h to allow drainage of the haematoma. After UFH was restarted on day 7, the platelet count continued to decrease (22 · 10/l) and was complicated by deep venous thrombosis (DVT) of the left arm 3 d later (Day 10). HIT was diagnosed on day 12, based on clinical data and a positive platelet aggregation test (80% aggregation in the presence of UFH (1 iu/ml) with 4/5 control platelets, no aggregation being seen with UFH at high concentration (100 iu/ml). An enzyme-linked immunosorbent assay to detect heparin platelet factor 4 antibodies was negative. The platelet count recovered (173 · 10/l) 6 d after UFH withdrawal. The precocious onset of thrombocytopenia (in the apparent absence of heparin treatment during the previous 100 d) prompted an initial diagnosis of catastrophic anti-phospholipid syndrome, the diagnosis of HIT being made only on day 12, in light of the positive platelet aggregation test and rapid recovery of the platelet count after heparin withdrawal. Alternative anticoagulant treatment was imperative. Considering the patient’s severe renal insufficiency (creatinine clearance of 35Æ5 ml/min) and the persistent risk of haemorrhage (related to the recent subdural haematoma), lepirudin was chosen to treat the HIT-related DVT, because of its short half-life. As the patient presented a spontaneously prolonged activated partial thromboplastin time and as this parameter does not show a sufficient response to lepirudin (Tardy et al, 2006), monitoring of lepirudin treatment based on anti-factor IIa levels was mandatory. An amidolytic anti-factor IIa assay that specifically evaluated direct thrombin inhibition (Walenga et al, 1991) was therefore used. To avoid extension of the cerebral haemorrhage, anti-factor IIa values were targeted around 0Æ5 lg/ml, as this was considered a safe therapeutic anticoagulation level. Lepirudin treatment was started at a low dose (0Æ0125 mg/kg/h), and reduced to 0Æ00025 mg/kg/h as renal failure worsened (creatinine clearance 18Æ4 ml/min) (Fig 1). These extremely low doses were nevertheless sufficient to maintain anti-factor IIa levels between 0Æ3 and 0Æ9 lg/ml,

TFPI resistance related to inherited or acquired protein S deficiency

BACKGROUND Protein S (PS) is an essential component of the protein C pathway and PS deficiency can explain a poor response to activated protein C. It has recently been shown that PS also acts as a cofactor of Tissue Factor Pathway Inhibitor (TFPI). OBJECTIVES In the present study, we investigated whether PS deficiency could be responsible for a poor response to TFPI. PATIENTS/METHODS Thirty-one patients with inherited PS deficiency, seven pregnant women and 36 controls were enrolled in the study. We measured the plasma response to added TFPI using a two-step diluted prothrombin time (dPT) assay. The response of the different plasmas to the anticoagulant activity of TFPI was expressed as TFPI Normalised Ratio (TFPI NR). RESULTS The median TFPI NR was statistically significantly lower in patients with inherited PS deficiency (0.5) than in controls (1.0) (p<0.0001). It was statistically significantly lower in patients with type I inherited PS deficiency (0.47) compared to patients with type III inherited PS deficiency (0.58) (p=0.018). In contrast, it did not differ between patients with and without thrombosis. Median TFPI NR values were statistically significantly lower during pregnancy (0.54) than 3 months after delivery (0.71) (p=0.016). TFPI NR values correlated well with PS activity values (R(2)=0.681) whatever the nature of the PS deficiency. CONCLUSIONS Our findings confirm that PS deficiency results in a poor anticoagulant response to TFPI, demonstrating again the cofactor role of PS in TFPI activity.

Effects of argatroban, danaparoid, and fondaparinux on trombin generation in heparin - induced thrombocytopenia

There is no in vitro data on the comparison of the effects of danaparoid, argatroban and fondaparinux on thrombin generation in patients with heparin-induced thrombocytopenia. It was the study objective to compare the in vitro anticoagulant potential of argatroban, danaparoid and fondaparinux using a thrombin generation assay TGA on a mixture of control platelet-rich plasma (PRP) and HIT patient platelet-poor plasma (PPP). The plasma of seven patients with a clear HIT diagnosed at our institution was selected. Mixtures of donor PRP and patient PPP were incubated with unfractionated heparin 0.2 U.mL⁻¹, argatroban at 600 ng.mL⁻¹, argatroban at 400 ng.mL⁻¹, danaparoid at 0.65 IU.mL⁻¹ and fondaparinux at 1 μg.mL⁻¹. Thrombin generation was assessed by calibrated thrombinography. The percentage of inhibition of the endogenous thrombin potential observed with argatroban at 600 ng.mL⁻¹ was statistically significantly higher compared with those observed with fondaparinux (median: 53.6% vs. 3.9%; p=0.031) but not compared with argatroban at 400 ng.mL⁻¹ and danaparoid. The percentage of inhibition of the thrombin peak observed with argatroban at 600 ng.mL⁻¹ was statistically significantly higher compared with those observed with danaparoid (median: 71.2 vs. 56.8; p=0.031) and fondaparinux (mean: 71.2 vs. 30; p=0.031) but not with argatroban at 400 ng.mL⁻¹. In conclusion, the in vitro effect of argatroban and danaparoid on thrombin generation seems to corroborate the results of clinical studies of these drugs in the treatment of HIT in term of efficiency. Fondaparinux showed a very small effect on thrombin generation evaluated by calibrated thrombinography.

Pentosan polysulfate induced thrombocytopenia and thrombosis

Pentosan polysulfate is a low-molecular-weight sulfated polysaccharide used as an antithrombotic drug. We present two patients who developed thrombocytopenia and venous thrombosis during treatment with pentosan polysulfate. The relationship between pentosan polysulfate and thrombocytopenia is supported by platelet aggregation and serotonin release tests. In the light of the literature and our two cases, it appears that pentosan polysulfate alone as standard heparin and low-molecular-weight heparin can induce thrombocytopenia and thrombosis. Platelet counts should therefore be periodically monitored during pentosan polysulfate treatment. In the case of pentosan polysulfate-induced thrombocytopenia, it seems that heparin or low-molecular-weight heparin should not be instituted during the acute phase even if platelet aggregation studies are negative, because of their low sensitivity. After remission of thrombocytopenia, whether or not glycosaminoglycans can be reinstituted, at least temporarily, after antibody had disappeared is still an open question.