Haemostatic changes in urogenital schistosomiasis haematobium: a case-control study in Gabonese schoolchildren.

In many tropical areas schistosomiasis is a major health problem causing hepatosplenic, intestinal or urogenital complaints. Hepatosplenic schistosomiasis mansoni is also characterized by blood coagulation abnormalities. Liver pathology plays a role in the development of haemostatic changes and the parasitic infection may directly affect coagulation. However, these contributing factors cannot be studied separately in hepatosplenic schistosomiasis infections. This pilot study provides insight in haemostatic changes in urinary schistosomiasis by studying coagulation parameters in schistosomiasis haematobium-infected Gabonese schoolchildren. Selection on urinary schistosomiasis patients without hepatosplenic complaints allows for the investigation of the direct effects of the parasite on haemostasis. Levels of von Willebrand Factor (VWF) antigen, active VWF and osteoprotegerin were elevated, indicating inflammation-mediated endothelial activation. In contrast to hepatosplenic schistosomiasis, thrombin-antithrombin complex and D-dimer levels were not affected. Despite its small sample size, this study clearly indicates that Schistosoma haematobium directly alters the activation status of the endothelium, without initiation of coagulation.

High prevalence of reduced thrombin generation and/or decreased platelet response in women with unexplained heavy menstrual bleeding.

INTRODUCTION: Heavy menstrual bleeding (HMB) is a condition that affects 20%-30% of women of reproductive age. HMB has a multifactorial pathophysiology, which is incompletely understood. HMB symptoms are very common in patients with established haemostasis defects, likewise, women with heavy menstrual bleeding have a higher prevalence of impaired Von Willebrand factor (VWF) levels and function, thrombocytopenia, impaired platelet function and impaired coagulation. The aim of this study was to quantify the prevalence of impaired platelet function, impaired coagulation and reduced VWF activity in patients with HMB. METHODS: We have used thrombin generation (TG), a flow cytometry-based platelet function test and a flow cytometry-based VWF function test to study haemostasis in 58 women (median age: 48.4 years, range 40-60 years) with HMB. In addition, we determined VWF antigen levels and VWF ristocetin co-factor activity in platelet-poor plasma. Reference ranges of platelet function were measured in whole blood of 123 healthy volunteers, while reference ranges of TG were determined in platelet-poor plasma (PPP) of 126 healthy volunteers. RESULTS: Fourteen (24%) patients with HMB had impaired platelet function and 17 (29.3%) patients had impaired coagulation. Five patients (8.6%) had both impaired platelet function and impaired coagulation. Only 2 (3.4%) patients had an impaired VWF function or levels; one of them was in combination with impaired coagulation. CONCLUSION: Our approach in women with HMB using a high precision platelet function test in combination with thrombin generation showed impaired coagulation or impaired platelet function in more than 40% of the patients.

Decreased plasma levels of activated factor VII in patients with deep vein thrombosis.

BACKGROUND: The initiating trigger in the development of deep vein thrombosis (DVT) remains unidentified. It has been suggested that tissue factor (TF)-bearing microparticles play a key role, which indicates a role for the TF pathway in the initiation of DVT. OBJECTIVE: To assess the role of the TF pathway in the initiation of venous thrombosis, we measured plasma levels of factor VII and VIIa in patients with acute DVT and in controls. METHODS: We included 148 patients diagnosed with acute DVT and 179 controls in this study. Antigen levels of FVII and FVIIa were measured by using assays recently developed in our laboratory. RESULTS: Median FVII levels in patients were 109.8% (interquartile range [IQR] 86.0-153.2) compared with 102.2% (IQR 76.1-141.7) in controls. Individuals with FVII levels in the upper quartile had a 1.6-fold increased risk for the presence of a DVT (odds ratio 1.6, 95% confidence interval 0.8-3.1). Median FVIIa levels in patients were 50.2 ng mL(-1) (IQR 25.2-86.1) compared with 96.6 ng mL(-1) (69.9-168.9) in controls. Individuals with FVIIa levels in the lowest quartile had a > 5-fold increased risk for the presence of a DVT (odds ratio 5.5, 95% confidence interval 2.8-10.6). Both risks did not change substantially after adjustment for potential confounders. CONCLUSION: Decreased plasma levels of FVIIa in patients with deep vein thrombosis may indicate ongoing consumption of FVIIa and suggest a contributory role for TF in venous thrombus formation.

Morbidity and mortality in the antiphospholipid syndrome during a 10-year period: a multicentre prospective study of 1000 patients.

OBJECTIVES: To assess the prevalence of the main causes of morbi-mortality in the antiphospholipid syndrome (APS) during a 10-year-follow-up period and to compare the frequency of early manifestations with those that appeared later. METHODS: In 1999, we started an observational study of 1000 APS patients from 13 European countries. All had medical histories documented when entered into the study and were followed prospectively during the ensuing 10 years. RESULTS: 53.1% of the patients had primary APS, 36.2% had APS associated with systemic lupus erythematosus and 10.7% APS associated with other diseases. Thrombotic events appeared in 166 (16.6%) patients during the first 5-year period and in 115 (14.4%) during the second 5-year period. The most common events were strokes, transient ischaemic attacks, deep vein thromboses and pulmonary embolism. 127 (15.5%) women became pregnant (188 pregnancies) and 72.9% of pregnancies succeeded in having one or more live births. The most common obstetric complication was early pregnancy loss (16.5% of the pregnancies). Intrauterine growth restriction (26.3% of the total live births) and prematurity (48.2%) were the most frequent fetal morbidities. 93 (9.3%) patients died and the most frequent causes of death were severe thrombosis (36.5%) and infections (26.9%). Nine (0.9%) cases of catastrophic APS occurred and 5 (55.6%) of them died. The survival probability at 10 years was 90.7%. CONCLUSIONS: Patients with APS still develop significant morbidity and mortality despite current treatment. It is imperative to increase the efforts in determining optimal prognostic markers and therapeutic measures to prevent these complications.

Plasma levels of active Von Willebrand factor are increased in patients with first ST-segment elevation myocardial infarction: a multicenter and multiethnic study.

AIMS: Von Willebrand factor (VWF), a key player in hemostasis and thrombosis, is released from endothelial cells during inflammation. Upon release, VWF is processed by ADAMTS13 into an inactive conformation. The aim of our study was to investigate whether plasma levels of active VWF, total VWF, ADAMTS13, osteoprotegerin (OPG) and the ratios between VWF and ADAMTS13 are risk factors for first ST-segment elevation myocardial infarction (STEMI). METHODS AND RESULTS: We assessed 1026 patients with confirmed first STEMI and 652 control subjects from China, Italy and Scotland, within six hours after their cardiovascular event. Median plasma levels of total VWF, active VWF, OPG and ratios VWF/ADAMTS13 were increased, while plasma levels of ADAMTS13 were decreased in patients compared to controls. The odds ratio (OR) of STEMI in patients with high plasma levels of active VWF was 2.3 (interquartile range (IQR): 1.8-2.9), total VWF was 1.8 (1.4-2.3), ADAMTS13 was 0.6 (05-0.8), OPG was 1.6 (1.2-2.0) and high VWF/ADAMTS13 ratios was 1.5 (1.2-2.0). The OR for total VWF, active VWF and ratios VWF/ADAMTS13 remained significant after adjustment for established risk factors, medical treatment, C-reactive protein, total VWF, ADAMTS13 and OPG. When we adjusted for levels of active VWF, the significance of the OR for VWF and ratios VWF/ADAMTS13 disappeared while the OR for active VWF remained significant. CONCLUSIONS: We found evidence that plasma levels of active VWF are an independent risk factor for first STEMI in patients from three different ethnic groups. Our findings confirm the presence of VWF abnormalities in patients with STEMI and may be used to develop new therapeutic approaches.

Increased factor XIa levels in patients with a first acute myocardial infarction: the introduction of a new thrombin generation based factor XIa assay.

OBJECTIVE: One of the contributing mechanisms in acute myocardial infarction (AMI) is plasma hypercoagulability. Recently, it was suggested that factor XI activation might play a role in atherothrombosis. To quantify factor XIa plasma levels, we developed a new thrombin generation based assay and hypothesized that in AMI patients factor XIa levels are increased during the acute thrombotic event. METHODS: A prospective cohort study was performed including 56 patients with first AMI. Blood was collected upon admission and after 6 months. Reference blood samples were obtained from 30 apparently healthy control subjects. Plasma samples were diluted (1:5) in factor XI deficient plasma and factor XIa plasma levels were established using a reference curve (0-12.5 pM factor XIa) and an inhibitory anti-factor XIa antibody. The established FXIa concentrations were related to the 1-year outcome. RESULTS: Factor XIa plasma concentrations were significantly increased in AMI patients on admission compared to 6 months after the event (3.7 pM [2.7-5.5] vs. 2.8 [1.9-4.3], median ± IQR; P=0.001) and compared to healthy controls (3.7 pM [2.7-5.5] vs. 2.7 [1.6-4.2], median ± IQR; P=0.004). However, a high factor FXIa level at baseline was not significantly associated with a recurrent cardiovascular event (OR 1.26, 95%CI 0.33-4.7). CONCLUSIONS: This study presents the first application of a new thrombin generation based factor XIa assay, showing significantly increased factor XIa levels in AMI patients on admission compared to 6 months after the event and compared to healthy controls. The factor XIa concentration was not associated with the risk of recurrence.

Cirrhosis patients have a coagulopathy that is associated with decreased clot formation capacity.

BACKGROUND: The coagulopathy in cirrhosis is associated with thrombosis and bleeding. OBJECTIVES: To gain better insights into the coagulopathy in patients with cirrhosis, we evaluated plasma thrombin generation and whole blood clot formation in a cross-sectional study. METHODS: Blood was collected from 73 patients with all-cause cirrhosis (Child-Pugh-A n = 52, B n = 15, C n = 6) and 20 healthy controls. Activity of the coagulation pathways was measured with assays for factor (F) VIIa and FIXa-antithrombin and FXa-antithrombin complexes, respectively. Thrombin generation by calibrated automated thrombography was determined in platelet-poor plasma using a 1 or 5 pm tissue factor trigger with/without thrombomodulin. ROTEM measurements were performed in whole blood triggered with 35 pm tissue factor without/with 175 ng mL(-1) tissue plasminogen activator (the latter refered to as 'tPA-ROTEM'). RESULTS: We observed an increased generation of FVIIa and a moderately elevated amount of FIXa (in complex with antithrombin) without apparent increase in FX activation in patients with cirrhosis. In accordance with this prothrombotic state, markers of thrombin generation potential were also increased upon increasing severity of cirrhosis. In the whole blood clotting assay we observed delayed clot formation and decreased clot strength associated with increased severity of cirrhosis. No significant differences were found for tPA-ROTEM parameters of clot degradation. CONCLUSION: These results indicate that cirrhosis patients have an overall procoagulant plasma milieu but a decreased whole blood clot formation capacity with an apparently unaltered resistance to clot lysis.

Platelet function alterations in dengue are associated with plasma leakage.

Severe dengue is characterised by thrombocytopenia, plasma leakage and bleeding. Platelets are important for preservation of endothelial integrity. We hypothesised that platelet activation with secondary platelet dysfunction contribute to plasma leakage. In adult Indonesian patients with acute dengue, we measured platelet activation status and the response to the platelet agonist TRAP using flow cytometer-based assays. Patients were monitored daily for plasma leakage by ultrasonography. Acute dengue was associated with platelet activation with an increased expression of the activated fibrinogen receptor (αIIbß3), the lysosomal marker CD63 and the alpha-granule marker CD62P (P-selectin). Upon maximal platelet activation by TRAP, platelet function defects were observed with a significantly reduced maximal activated αIIbß3 and CD63 expression and reduced platelet-monocyte and platelet-neutrophil complexes. Patients in the lowest tertile of activated αIIbß3 and CD63 expression had an odds ratio for plasma leakage of 5.2 (95% confidence interval [CI] 1.3-22.7) and 3.9 (95% CI 1.1-13.7), respectively, compared to the highest tertile. Platelet-derived serotonin has previously been related to plasma leakage and we found increased intra-platelet serotonin concentrations in our patients. In conclusion, platelet activation with platelet function alterations can be found in patients with acute dengue and this may contribute to dengue-associated plasma leakage.

Sustained pro-haemostatic activity of rFVIIa in plasma and platelets in non-bleeding pigs may explain the efficacy of a once-daily prophylaxis in humans.

Recombinant factor VIIa (rFVIIa) is registered for treatment of inhibitor-complicated haemophilia, and a once-daily prophylactic administration of rFVIIa is successful in reducing the number of bleeding events. This suggests that a single rFVIIa dose has a pro-haemostatic effect up to 24 hours (h), which is difficult to explain given its half-life of 2 h. In this study, six pigs received a 90 µg/kg rFVIIa bolus. Plasma was collected and platelets were isolated at various time points up to 48 h, and analysed for FVIIa levels and associated haemostatic activity. Elevated plasma FVIIa levels were detected up to 24 h post-administration (36 (32-56) mU/ml [median (interquartile range [IQR]), 24 h] vs 2 (2-14) mU/ml [baseline]). Corresponding prothrombin time (PT) values remained shortened compared to baseline until 24 h post-administration (9.4 (9.3-9.9) seconds (s) [24 h] vs 10.5 (10.2-11.0) s [baseline], p ≤0.01). The lag time in thrombin generation testing as well as clotting times in plasma-based assays were shortened up to 12 or 24 h post-administration, respectively (lag times 1.8 (1.7-2.1) minutes (min) [12 h] vs 2.3 (2.3-2.6) min [baseline], p ≤0.01 and clotting times 3.8 (3.2-3.9) min [24 h] vs 5.2 (4.6-5.5) min [baseline], p ≤0.001). Platelet FVIIa levels were elevated up to 48 h (7.7 (3.4-9.0) ng VIIa/mg actin [48 h] vs 2.5 (0.7-4.8) ng VIIa/mg actin [baseline]). In conclusion, elevated and haemostatically active plasma and platelet FVIIa levels are detectable up to 24-48 h following rFVIIa administration in pigs. This prolonged pro-haemostatic effect of FVIIa may explain the prophylactic efficacy of a once-daily rFVIIa treatment.

Platelet-reactivity tests identify patients at risk of secondary cardiovascular events: a systematic review and meta-analysis.

BACKGROUND: Antiplatelet therapy is the standard treatment for the prevention of cardiovascular events (CVEs). High on-treatment platelet reactivity (HPR) is a risk factor for secondary CVEs in patients prescribed aspirin and/or clopidogrel. The present review and meta-analysis was aimed at assessing the ability of individual platelet-function tests to reliably identify patients at risk of developing secondary CVEs. METHODS AND RESULTS: A systematic literature search was conducted to identify studies on platelet-reactivity measurements and CVEs. The main inclusion criteria were: (i) prospective study design; (ii) study medication, including aspirin and/or clopidogrel; and (iii) a platelet-function test being performed at baseline, before follow-up started. Of 3882 identified studies, 102 (2.6%; reporting on 44 098 patients) were included in the meta-analysis. With regard to high on-aspirin platelet reactivity (HAPR), 22 different tests were discussed in 55 studies (22 441 patients). Pooled analysis showed that HAPR was diagnosed in 22.2% of patients, and was associated with an increased CVE risk (relative risk [RR] 2.09; 95% confidence interval [CI] 1.77-2.47). Eleven HAPR tests independently showed a significantly increased CVE risk in patients with HAPR as compared with those with normal on-aspirin platelet reactivity. As regards high on-clopidogrel platelet reactivity (HCPR), 59 studies (34 776 patients) discussed 15 different tests, and reported that HCPR was present in 40.4% of patients and was associated with an increased CVE risk (RR 2.80; 95% CI 2.40-3.27). Ten tests showed a significantly increased CVE risk. CONCLUSIONS: Patients with HPR are suboptimally protected against future cardiovascular complications. Furthermore, not all of the numerous platelet tests proved to be able to identify patients at increased cardiovascular risk.

Factor VIII concentrate infusion in patients with haemophilia results in decreased von Willebrand factor and ADAMTS-13 activity.

The effects of coagulation factor concentrate infusion on restoring secondary haemostasis in patients with haemophilia are obvious. It is not known whether coagulation factor concentrate infusion affects primary haemostasis or induces an acute inflammatory response. In this study, the influence of a factor VIII (FVIII) concentrate bolus infusion on platelet activation and responsiveness, endothelial activation, and inflammation in adult patients with severe haemophilia A was assessed. VWF showed a mild, but significant decrease 15 min after FVIII infusion (85.02 IU dL(-1)) vs. before infusion (92.04 IU dL(-1) ; P = 0.017), while ADAMTS-13 levels also show a mild but significant decrease from 66.1 ng mL(-1) before infusion, to 53.9 ng mL(-1) (P = 0.012) 15 min after and 50.8 ng mL(-1) (P = 0.050) 60 min after infusion. Platelet P-selectin expression decreased 15 min (33.3 AU) and 60 min (38.7 AU) after infusion compared to before infusion (41.3 AU; P = 0.018 and 0.036). In conclusion, a single infusion of a high dose FVIII concentrate in haemophilia A patients may influence primary haemostasis by decreasing VWF, ADAMTS-13 and the number of circulating activated platelets. These effects possibly occur as a consequence of binding of the infused FVIII to VWF, influencing its processing. When treating severe haemophilia A patients with coagulation concentrate infusion, one should realize this does not merely correct FVIII levels but also may influence primary haemostasis.

Increased cytokine response after toll-like receptor stimulation in patients with stable coronary artery disease.

OBJECTIVE: Atherosclerosis is associated with increased levels of plasma cytokines and expression of Toll-like receptors (TLRs). Yet, little is known about the potential use of TLR ligand induced cytokine release as a biomarker of coronary artery disease (CAD). In this study, we investigated whether TLR ligand induced cytokine release is associated with atherosclerotic disease severity and its predictive value for future cardiovascular events. METHODS: Blood samples were obtained from 260 patients with stable angina and 15 healthy controls. Cytokine levels of TNFα, IL-8 and IL-6 were measured after 2 h of whole blood stimulation with 10 ng/ml lipopolysaccharide (LPS, TLR4 ligand) and P3C 500 ng/ml (TLR2 ligand). In a subgroup, dose-response curves were created using additional LPS concentrations. RESULTS: LPS induced whole blood release of TNFα and IL-6, but not IL-8, was significantly higher in patients compared to healthy controls. Among CAD patients, TLR responses did hardly differ when associated with the presence of traditional risk factors and atherosclerotic disease severity (number of diseased vessels and coronary stenosis degree). Patients with secondary events during follow-up showed a trend towards an increased TLR response. Furthermore, positive associations were found between CRP levels and TLR-induced TNFα (CRP<2: 2055 pg/ml; CRP>2: 2364 pg/ml) and IL-6 production (CRP<2: 1742 pg/ml; CRP>2: 2250 pg/ml). CONCLUSION: In conclusion, TLR-induced whole blood cytokine release in patients with stable angina indicates the presence of coronary atherosclerosis but does not reflect its severity.

Increased mortality in systemic inflammatory response syndrome patients with high levels of coagulation factor VIIa.

BACKGROUND: The tissue factor (TF)- Factor VIIa (FVIIa) complex has a pivotal role in inflammatory and coagulation responses in patients with systemic inflammatory response syndrome (SIRS) and sepsis. Because zymogen FVII (FVII) and FVIIa compete for binding to TF, their plasma levels determine if a catalytically active TF-FVIIa complex will be formed. OBJECTIVE: To study mortality in SIRS patients as a function of FVIIa and FVII levels in plasma. METHODS: This was a cohort study of 275 patients presenting with SIRS, aged 18 years or older and with an anticipated Intensive Care Unit (ICU) stay of at least 24 h. FVIIa was measured using a novel, quantitative assay that recognizes FVIIa, but not FVII. All-cause hospital mortality was followed over a period of 60 days. RESULTS: The percentage of FVII measured as FVIIa was higher in non-survivors than survivors (2.8%, IQR = 1-5.5% vs. 1.5%, IQR = 0.6-3.3%; P = 0.034). High levels of FVIIa were associated with decreased 60-day cumulative survival (62% vs. 81%, P = 0.030); the opposite was observed for FVII (84% vs. 76%, P = 0.039). Patients with high-FVIIa and low-FVII levels had a three-fold increased hazard ratio (HR) compared with the patients that had low-FVIIa and high-FVII levels (HR = 3.24, 95% confidence interval [CI] = 1.41-7.36). This association persisted after adjusting for the APACHE IV score (adjusted HR = 2.75, 95% CI = 1.2-6.27). CONCLUSIONS: SIRS patients with high-FVIIa and low-FVII on admission have an increased mortality risk, an association that is independent from the parameters included in the APACHE IV score.

A nanobody-based method for tracking factor XII activation in plasma.

The physiological role of the plasma protein factor XII (FXII), as well as its involvement in human pathology, is poorly understood. While FXII is implicated in thrombotic pathology as a coagulation factor, it can contribute to inflammatory conditions without triggering coagulation. We recently generated nanobodies against the catalytic domain of activated FXII (FXIIa). Here, we describe two of these nanobodies, A10 and B7, both of which do not recognise FXII. Nanobody A10 recognises the catalytic domain of purified α-FXIIa (80 kDa), but not that of purified ß-FXIIa (28 kDa), whereas nanobody B7 recognises both. This suggests minute differences in the catalytic domain between these isoforms of FXIIa. The detection of FXIIa by these nanobodies in plasma can become compromised through inactivation by serine protease inhibitors. This effect can be efficiently countered through the addition of the small-molecular protease inhibitor PPACK. Finally, we show that our nanobody-based assays in vitro distinguish various activation products of FXII that differ with the type of activator present: whereas procoagulant activators solely trigger the formation of a species that is captured by B7, proinflammatory activators first generate a species that is recognised by B7, which is later converted into a species that is recognised by A10. These findings suggest that a progressive proteolysis of FXIIa results in the generation a non-procoagulant form of FXIIa, whereas retention of intermediate forms triggers coagulation. Moreover, our findings indicate the development of nanobodies against activated enzymes offers improved opportunities to investigate their contribution to health and disease.

Pathophysiology of thrombotic APS: where do we stand?

The antiphospholipid syndrome (APS) is diagnosed when patients with thrombotic complications or foetal losses have elevated levels of antiphospholipid antibodies in their plasmas. The term APS is confusing, because the pathogenic auto-antibodies are not directed against phospholipids but towards a plasma protein, ß(2)-glycoprotein I. For many years the reason why auto-antibodies against ß(2)-glycoprotein I were pro-thrombotic was unclear, because man and mice deficient in ß(2)-glycoprotein I do not express a clear phenotype. Animal models in which passive transfer of patient antibodies into mice resulted in an increased thrombotic response have provided novel insights in the importance of this protein in the pathology of APS.

Thrombogenicity of a new injectable biocompatible elastomer for aneurysm exclusion, compared to expanded polytetrafluoroethylene in a human ex vivo model.

OBJECTIVES: Customized aortic repair (CAR) is a new concept for endovascular aortic aneurysm repair in which a non-polymerised elastomer is injected to fill the aneurysm sac around a balloon catheter. Amongst other variables, the thrombogenicity of the elastomer should be tested, before further clinical experiments can take place. The aim of this human ex vivo study was to measure the thrombogenicity of the elastomer and to compare it to expanded polytetrafluoroethylene (ePTFE). DESIGN AND MATERIALS: In a validated ex vivo model, non-anticoagulated blood was drawn from the antecubital veins of 10 healthy donors with a 19-gauge needle. It was drawn through elastomer tubes and through ePTFE Gore-Tex vascular grafts, both 60 cm long and with an inner diameter of 3 mm. METHODS: Fibrinopeptide A (FPA) and P-selectin expression was measured in blood samples, collected at the end of the grafts. After the experiments, the deposition of platelets and fibrin onto the grafts was visualised by scanning electron microscopy. RESULTS: For these graft types, a progressive increase in FPA production was observed in time. No significant difference was observed between the elastomer and ePTFE grafts (p > 0.05). No increase in P-selectin expression, and thereby no platelet activation, was observed in the perfusate of either grafts (p > 0.05). By scanning electron microscopy, numerous platelet aggregates were observed on the ePTFE grafts, whereas just a few adhered platelets and no aggregates were observed in the elastomer grafts. CONCLUSIONS: The elastomer in its current formulation has a low thrombogenicity, comparable to ePTFE, making it an ideal substance for endovascular aneurysm sac filling. Further research should clarify the feasibility of CAR in vivo.

Recent developments in our understanding of the antiphospholipid syndrome.

The antiphospholipid syndrome is an autoimmune disease that manifests clinically as recurrent thrombotic complications or foetal losses and serologically with elevated levels of antiphospholipid antibodies in the plasmas of these patients. The term 'antiphospholipid syndrome' is confusing, because the auto-antibodies are not directed against phospholipids but towards a plasma protein, ß(2) -glycoprotein I. For many years, the reason why auto-antibodies against ß(2) -glycoprotein I were pro-thrombotic was unclear, because ß(2) -glycoprotein I seems to be an obsolete protein in our circulation. Human and mice deficient in this protein do not express a clear phenotype. Recent studies on the structure and function of ß(2) -glycoprotein I have provided novel insights into the importance of this protein in physiology and its role in the pathology of the antiphospholipid syndrome.

Lupus anticoagulant: performance of the tests as recommended by the latest ISTH guidelines.

OBJECTIVES: Lupus anticoagulant (LA) is clinically the most relevant among all antiphospholipid antibody tests. Recently, new guidelines for LA detection were published. The objective of this retrospective cohort study was to compare tests recommended under these guidelines with other methods used for LA detection. METHODS: The study group consisted of 336 subjects suffering from various autoimmune diseases. We used activated partial thromboplastin time (aPTT), diluted Russell viper venom time (dRVVT) and diluted prothrombin time (dPT) tests for LA detection together with a ratio between sensitive and insensitive aPTT reagent. We also tested if LA was dependent on ß(2) glycoprotein I (ß(2) GPI) using one of the recently described methods. RESULTS: All LA tests performed were associated with a history of thrombosis. The highest odds ratio (OR) for thrombosis was found for ß(2) GPI-dependent LA but sensitivity was low (OR = 8.4; specificity/sensitivity = 98%/15%). All LA tests showed a much stronger association with thrombosis than with pregnancy failure. CONCLUSIONS: LA tested by aPTT and/or dRVVT (at least one out of two tests positive), as recommended by the guidelines, was associated less strongly with a history of thrombosis (OR = 4.1) than either of these tests separately (OR = 5.0 and 4.3, respectively). With both tests positive ('double LA positivity') the association with thrombosis was stronger (OR = 6.5) compared with only one positive test. In fact, 'double LA positivity', detected by combinations of any of the tests studied, was markedly associated with a history of thrombosis.