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Hepatology 01/2013; · 11.66 Impact Factor
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ABSTRACT: We propose that porto-pulmonary hypertension (PPH) may arise as a consequence of deficiency of ADAMTS13 (a plasma metalloprotease that regulates von Willebrand factor size and reduces its platelet adhesive activity) and provide a clinical case history to support our hypothesis A patient with non-cirrhotic intrahepatic portal hypertension (NCIPH), ulcerative colitis and celiac disease developed symptoms of PPH which had advanced beyond levels which would have made her an eligible candidate for liver transplantation (mean pulmonary artery pressure (PAP) 49 mm Hg). She was known to have severe ADAMTS13 deficiency, which we considered to be causative of, or contributory to her NCIPH. We postulated that increasing porto-systemic shunting associated with advancing portal hypertension would make the next encountered vascular bed, the lung, susceptible to the pathogenic process that was previously confined to the portal system, with pulmonary hypertension as its consequence. Her pulmonary artery pressures fell significantly during the next year on weekly replacement of plasma ADAMTS13 by infusions of fresh frozen plasma and conventional drug treatment of her pulmonary hypertension. Her pulmonary artery pressures had fallen to acceptable levels when, in response to platelet infusion, it rose precipitously and dangerously. The sequence strongly supports our hypothesis that PPH is a consequence of ADAMTS13 deficiency and is caused by platelet deposition in afferent pulmonary vessels.
Journal of Hepatology 11/2012; · 9.26 Impact Factor
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British Journal of Haematology 02/2012; · 4.94 Impact Factor
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ABSTRACT: The guideline writing group was selected to be representative of UK-based medical experts. MEDLINE was systematically searched for publications in English up to the Summer of 2010 using key words platelet, platelet function testing and platelet aggregometry. Relevant references generated from initial papers and published guidelines/reviews were also examined. Meeting abstracts were not included. The writing group produced the draft guideline, which was subsequently revised and agreed by consensus. Further comment was made by members of the Haemostasis and Thrombosis Task Force of the British Committee for Standards in Haematology. The guideline was then reviewed by a sounding board of approximately 40 UK haematologists, the British Committee for Standards in Haematology (BCSH) and the British Society for Haematology Committee and comments incorporated where appropriate. Criteria used to quote levels and grades of evidence are as outlined in appendix 7 of the Procedure for Guidelines Commissioned by the BCSH [http://www.bcshguidelines.com/BCSH_PROCESS/EVIDENCE_LEVELS_AND_GRADES_OF_RECOMMENDATION/43_GRADE.html]. The objective of this guideline is to provide healthcare professionals with clear guidance on platelet function testing in patients with suspected bleeding disorders. The guidance may not be appropriate to patients receiving antiplatelet therapy and in all cases individual patient circumstances may dictate an alternative approach.
British Journal of Haematology 07/2011; 155(1):30-44. · 4.94 Impact Factor
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Anastasia Lambrianides,
Tabitha Turner-Stokes,
Charis Pericleous,
Jasmine Ehsanullah,
Eva Papadimitraki,
Katie Poulton,
Yiannis Ioannou,
Andrew Lawrie, Ian Mackie,
Pojen Chen,
David Latchman,
David Isenberg,
Anisur Rahman,
Ian Giles
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ABSTRACT: To characterize the interaction between procoagulant and/or anticoagulant serine proteases and human monoclonal IgG antiphospholipid antibodies (aPL) and polyclonal IgG derived from patients with the antiphospholipid syndrome (APS).
Five human monoclonal IgG with small differences in their sequences were tested for binding to protein C, activated protein C, plasmin, factor VIIa (FVIIa), FIX, FIXa, and FXII. Serum levels of antithrombin and anti-activated protein C were compared in 32 patients with APS, 29 patients with systemic lupus erythematosus (SLE), and 22 healthy controls. Purified polyclonal IgG derived from APS patients with elevated levels of serum antithrombin antibodies was also tested for its functional effects on thrombin and antithrombin activity.
Studies of monoclonal antibodies showed that sequence changes in human aPL are important in determining their ability to bind procoagulant and anticoagulant/fibrinolytic serine proteases. Mean IgG antithrombin levels were significantly elevated in patients with APS and in SLE patients with aPL but no APS (SLE/aPL+) compared to healthy controls, but anti-activated protein C levels were not increased in these patients. Moreover, IgG purified from patients with APS displayed higher avidity for thrombin and significantly inhibited antithrombin inactivation of thrombin compared with IgG from SLE/aPL+ patients.
High-avidity antithrombin antibodies, which prevent antithrombin inactivation of thrombin, distinguish patients with APS from SLE/aPL+ patients, and thus may contribute to the pathogenesis of vascular thrombosis in APS.
Arthritis & Rheumatism 07/2011; 63(11):3512-21. · 7.87 Impact Factor
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British Journal of Haematology 05/2011; 155(5):620-2. · 4.94 Impact Factor
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ABSTRACT: ADAMTS13 deficiency leading to excess ultralarge von Willebrand factor (VWF) multimers and platelet clumping is typically found in thrombotic thrombocytopenic purpura (a type of thrombotic microangiopathy). Idiopathic noncirrhotic intrahepatic portal hypertension (NCIPH) is a microangiopathy of portal venules associated with significant thrombocytopenia and predisposing gut disorders.
To determine whether the portal microangiopathy in NCIPH is associated with ADAMTS13 deficiency.
Plasma levels of ADAMTS13, anti-ADAMTS13 antibodies, and VWF were compared between cases (NCIPH patients) and controls (with chronic liver diseases of other etiology) matched for severity of liver dysfunction. Eighteen NCIPH patients [median (range) MELD score 12 (7-25)] and 25 controls [MELD score 11 (4-26)] were studied.
ADAMTS13 activity was reduced in all 18 NCIPH patients and significantly lower than controls (median, IQR: 12.5%, 5-25% and 59.0%, 44-84%, respectively, P<0.0001) [normal range for plasma ADAMTS13 activity (55-160%)]. ADAMTS13 activity was <5% in 5/18 NCIPH patients (28%) and 0/25 controls (P=0.009). ADAMTS13 antigen levels were also decreased. Sustained low ADAMTS13 levels were seen in four NCIPH patients over 6 weeks to 11 months (highest ADAMTS13 level in each patient: <5%, 6%, 6%, and 25%), despite two patients having MELD score 12. Although nine cases had low titer anti-ADAMTS13 antibodies, there was no significant difference between cases and controls. Abnormally large VWF multimers were observed in 4/11 NCIPH patients (36%) and in 0/22 controls (P=0.008).
Sustained deficiency of ADAMTS13 appears characteristic of NCIPH, irrespective of severity of liver disease.
Digestive Diseases and Sciences 05/2011; 56(8):2456-65. · 2.12 Impact Factor
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Trevor Baglin,
Elaine Gray,
Mike Greaves,
Beverley J Hunt,
David Keeling,
Sam Machin, Ian Mackie,
Mike Makris,
Tim Nokes,
David Perry,
R C Tait,
Isobel Walker,
Henry Watson
British Journal of Haematology 04/2010; 149(2):209-20. · 4.94 Impact Factor
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ABSTRACT: Thrombotic thrombocytopenic purpura (TTP) is an acute, rare, life-threatening disorder. This report presents the South East (SE) England registry for TTP, from April 2002 to December 2006, which included 176 patients and 236 acute episodes; 75% of patients were female and 25% were male, overall median age at presentation was 42 years. Mortality was 8.5%, most cases died before treatment was instigated. The main ethnic groups were Caucasian (64%) and Afro Caribbean (27%). Seventy-seven percent of cases were idiopathic, 5% were congenital and the remaining cases had a defined precipitant. Neurological features were the most prevalent, but cardiac involvement accounted for 42% of presenting features. The overall median number of plasma exchanges (PEXs) to remission was 15; between April 2002 and December 2003, the median number of PEXs was 19 and it was 12 between January 2004 and December 2006 (P < 0.0001). In the latter period, adjuvant therapies were reduced, but Rituximab was increased. ADAMTS 13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) activity was <10% in 74% and 95% of these cases had positive IgG antibodies to ADAMTS 13. Renal impairment and delayed normalisation of platelet count were the main differences between idiopathic and secondary TTP.
British Journal of Haematology 09/2008; 142(5):819-26. · 4.94 Impact Factor
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Maxwell Westerman,
Arnold Pizzey,
Jocelyn Hirschman,
Mario Cerino,
Yonit Weil-Weiner,
Prya Ramotar,
Ada Eze,
Andrew Lawrie,
Gordon Purdy, Ian Mackie,
John Porter
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ABSTRACT: Levels of circulating red blood cell (RBC)-derived vesicles are increased in sickle cell anaemia (SCA) and thalassaemia intermedia (TI) but the mechanisms, effects and controlling factors may differ. This study found that levels of vesicles and intravascular haemolysis were linked as shown by the correlation between levels of vesicles and plasma Hb. Vesicle levels were 6-fold greater in SCA and 4-fold greater in TI than in controls. The proportion of plasma Hb within vesicles was increased in SCA and TI with a significantly higher proportion in TI. We examined whether subpopulations of RBC expressing phosphatidylserine (PS) were a source of PS(+) vesicles and observed a significant association. Thrombin generation was promoted by the vesicles in which 40-50% expressed PS. In TI, markers of thrombin generation were significantly related to PS(+) RBC. Splenectomy in TI had significant effects including greater increases in vesicle levels, plasma Hb, PS(+) RBCs and thrombin generation markers than in unsplenectomised patients. In hydroxycarbamide (HC)-treated SCA patients these measures were decreased compared with untreated controls. The relationship between vesicle levels and plasma Hb suggests a mechanism linking vesiculation to haemolysis and consequently nitric oxide (NO) bioavailability and suggests a means by which HC treatment improves NO bioavailability.
British Journal of Haematology 08/2008; 142(1):126-35. · 4.94 Impact Factor
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ABSTRACT: This guideline provides a framework for the arrangement of point-of-care testing (POCT) services, previously known as near patient testing (patient self-testing not covered). POCT is defined as any analytical test performed outside the laboratory. Primary users are often non-laboratory healthcare workers. The guidance applies to units within hospitals as well as general practioner surgeries, community clinics and pharmacies. The head of the haematology laboratory or a point of care coordinator must take responsibility for all aspects of the POCT service, including quality and training. Depending on the size and nature of the POCT practice, a local POCT manager may also be required. Equipment selected should have received a successful independent performance evaluation. If an independent evaluation has not been performed the purchaser should assess the device according to the protocol in this document. POCT devices should generate results that are comparable to those of the local laboratory. An accredited external quality assessment programme and internal quality control system must be established. Manufacturers promoting POCT devices designed for non-laboratory sites, e.g. pharmacies, should undertake training and annual competency assessment, perhaps using a web-based system. A diagram to illustrate the stages for the implementation of a POCT service is illustrated.
British Journal of Haematology 08/2008; 142(6):904-15. · 4.94 Impact Factor
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ABSTRACT: Reduced plasma survival of von Willebrand factor (VWF) may contribute towards the pathogenesis of type 1 von Willebrand disease (VWD). However, little is known about mechanism(s) of VWF clearance and factors that may affect it. The half-life of VWF-related parameters following the administration of DDAVP was measured in 26 patients with type 1 VWD and 10 haemophilia A controls. Binding of lectins Ricinus communis (RCA-I) and Erythina crystagalli (ECA) agglutinins to VWF and VWF susceptibility to ADAMTS-13-mediated proteolysis were investigated. Sequence analysis of targeted regions of the VWF gene was performed to inspect for mutations that have been associated with increased clearance. Post-DDAVP clearance of VWF was increased approximately three-fold in the type 1 VWD cohort overall. However this was not shown to consistently associate with steady-state VWF antigen (VWF:Ag) levels. Furthermore, increased VWF clearance was not consistently associated with increased ratios of VWF propeptide (VWFpp) to VWF:Ag indicating that a normal ratio does not necessarily reflect normal post-DDAVP survival in type 1 VWD patients. RCA-I and ECA binding to VWF were increased in type 1 VWD patients and, although inversely correlated with VWF levels, this was independent of VWF clearance. There was no association between VWF clearance and ADAMTS-13-mediated proteolysis. Three novel candidate mutations with an increased clearance phenotype were identified. The data are consistent with heterogeneity in pathogenic mechanisms in type 1 VWD and are consistent with type 1 VWD representing a complex genetic trait.
Thrombosis and Haemostasis 06/2008; 99(5):916-24. · 5.04 Impact Factor
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ABSTRACT: The consequences of an erroneous thrombophilia diagnosis may be serious if it is used to determine clinical management. Therefore careful selection, assessment, and control of laboratory tests for thrombophilia are essential. As for other coagulation tests, the pre-analytical phase must be carefully controlled with attention to the specific problems associated with each type of assay. The investigator must then recognize that for most laboratory tests of thrombophilia, there are a number of assay types available, often based on different principles of analysis. This creates the potential for different users to obtain varying results depending on the technique employed. Such problems can occur in assays of antithrombin activity, depending on whether the assay employs factor Xa, human thrombin, or bovine thrombin. In clot-based assays of protein C and protein S, there can be specificity problems related to interference by factor V Leiden (FVL), antiphospholipid antibodies, and other substances. Even genetic tests can give erroneous results and should not automatically be seen as absolute without supporting evidence and careful quality-control measures. Whatever technique is selected, it is mandatory to incorporate sufficient concurrent quality-control samples to validate the results of thrombophilia tests. These should include assessment of the parameter at normal and abnormal levels to give confidence in results across the measurement range that would normally be encountered in routine practice. This should be used in conjunction with regular participation in external quality assessment (EQA) (which has been linked to improved laboratory performance in thrombophilia testing). Larger EQA programs can provide information concerning the relative performance of analytical procedures, including the method principle, reagents, and instruments. Herein, we describe many of the methodologic effects in detail. We use specific examples to illustrate the general principle that, in performing laboratory testing for thrombophilia, one must always consider the performance characteristics and limitations of the assay in use.
Seminars in Hematology 05/2007; 44(2):114-25. · 3.99 Impact Factor
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ABSTRACT: Thrombotic thrombocytopenic purpura (TTP) has been linked to a severe deficiency in ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 motif, member 13) activity. Since the identification of ADAMTS13, and its target cleavage sequence in von Willebrand factor (VWF), several novel ADAMTS13 activity, antigen and autoantibody assays have been developed. Our aim was to evaluate the potential use of these novel assays. ADAMTS13 activity and inhibitors were measured by overnight incubation of patient plasma with pure VWF followed by multimer or collagen binding analysis. ADAMTS13 activity (Rapid peptide assay), antigen and immunoglobulin G anti-ADAMTS13 were measured by enzyme-linked immunosorbent assay. 118 samples from seven TTP patients (six adult idiopathic, one congenital) were studied longitudinally during episodes of TTP, their treatment and prophylaxis. ADAMTS13 antigen levels varied considerably between patients and sample times, but in new cases of acute TTP, rapid assays of ADAMTS13 antigen, on serial samples, maybe helpful in confirming the diagnosis. The rapid peptide ADAMTS13 activity assay showed good concordance of results with the older activity assay methods. The change in ADAMTS13 activity mirrored the autoantibody level and in 5/6 acquired TTP cases, a fall in antibody appeared to predict a rise in ADAMTS13 activity, potentially allowing modification of patient management based on autoantibody levels.
British Journal of Haematology 03/2007; 136(4):649-55. · 4.94 Impact Factor
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ABSTRACT: Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disorder and plasma exchange (PEX) remains the primary treatment modality. Twenty-five patients with acute refractory/relapsing idiopathic TTP received rituximab in conjunction with PEX because of progressive clinical disease or deterioration in laboratory parameters, despite intensive standard therapy. In relapsing TTP, rituximab was started if antibody to ADAMTS-13 (a disintegrin and metalloproteinase with thrombospondin motif-13) was demonstrated during previous episodes. All 25 patients attained complete clinical and laboratory remission in a median of 11 d after initiating rituximab. In 21 cases, ADAMTS-13 activity was within the normal range following rituximab. Inhibitors were detected in 24/25 patients by mixing studies and/or immunoglobulin G (IgG) antibodies to ADAMTS-13 pre-rituximab. There was no evidence of inhibitors and/or IgG activity <10% in 23/25 patients following rituximab. In acute refractory cases, the median number of PEX pre-rituximab and following the first rituximab infusion was 13 and 9, respectively. There have been no infectious complications, despite low CD 19 levels and no relapses. In patients with acute refractory/relapsing idiopathic TTP, rituximab appears to be a safe, effective, targeted therapy with a significant reduction in the requirement for PEX.
British Journal of Haematology 03/2007; 136(3):451-61. · 4.94 Impact Factor
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ABSTRACT: Pregnancy is an initiating event for acute thrombotic thrombocytopaenic purpura (TTP). There is a high risk of relapse during pregnancy and of foetal morbidity. We describe five cases with successful maternal and foetal outcomes in patients with a history of TTP. Cases 1 and 2 presented with TTP in their first pregnancy and had second-trimester foetal losses. Case 3 had four TTP relapses and soon after achievement of clinical remission became pregnant. Case 4 presented with TTP and left-sided stroke in pregnancy. ADAMTS-13 activity was less than 5% at presentation in four patients and prior to therapy during pregnancy in cases 1-4. Case 5, who had a single acute episode of TTP and became pregnant 6 years later, had normal ADAMTS-13 activity throughout pregnancy. Only case 3 had evidence of an inhibitor on mixing studies. All five patients underwent close haematological and obstetric monitoring and continued low-dose aspirin throughout pregnancy. Patients 1-4 had regular plasma exchange and received low molecular weight heparin during pregnancy. Patient 4 also received rituximab during the third trimester with no observed maternal or neonatal toxicity. Live healthy infants were delivered in all five cases in the third trimester. These findings suggest that successful pregnancy outcome is achievable in patients with a history of TTP and that patients with severely reduced ADAMTS-13 activity at the onset of pregnancy, necessitates regular plasma exchange during pregnancy.
Blood Coagulation and Fibrinolysis 10/2006; 17(6):459-63. · 1.24 Impact Factor
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ABSTRACT: Previous studies have demonstrated shortened bleeding times in patients with acute coronary syndromes, especially in myocardial infarction (MI). In this study we have investigated platelet hyper-function using the PFA-100 with collagen/adenosine diphosphate and collagen/epinephrine cartridges in 78 patients presenting with acute chest pain. Patients were classified into MI, unstable angina (UA) and non-specific chest pain. All patients received 300 mg aspirin (ASA) more than 2 h before blood samples were collected. Twenty healthy normal subjects were also tested before and 2 h after 300 mg ASA (n = 10). The collagen/adenosine diphosphate closure time was significantly shorter in MI patients (median, 71 s; P = 0.0237) but not in UA patients (median, 81 s; P > 0.05) compared with normal subjects (median, 92.5 s). The collagen/epinephrine closure times were significantly longer in UA patients (median, 233 s) than in untreated controls (median, 125 s; P < 0.0001), as expected, but there was no difference in MI patients (median, 149.24 s; P > 0.05), suggesting that the MI patients were not all responding to ASA. Analysis of a subset of the apparent ASA non-responders (n = 5) by platelet aggregation demonstrated that this was not related to failure of ASA to block cyclo-oxygenase activity. Von Willebrand factor levels were significantly elevated in both UA and MI patients compared with normal subjects (mean, 175.5 and 248.9 versus 89.1 s; P < 0.0001 and P < 0.0001, respectively) and were also significantly higher in the MI group compared with the UA group (P < 0.05). There is evidence for platelet hyper-function and elevated von Willebrand factor levels in the MI group that could explain their decreased responsiveness to ASA on the collagen/epinephrine cartridge.
Blood Coagulation and Fibrinolysis 11/2005; 16(8):557-62. · 1.24 Impact Factor
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British Journal of Haematology 11/2003; 123(2):372-3. · 4.94 Impact Factor
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Transfusion 06/2003; 43(5):677-8; author reply 678. · 3.22 Impact Factor
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ABSTRACT: The neuronal prion protein (PrPC) is also expressed within peripheral tissues including human blood. The majority of blood PrPC is found within the plasma fraction. We hypothesized that the vascular endothelium could be a source of this PrPC. Reverse transcription polymerase chain reaction demonstrated that both human umbilical vein endothelial cells (HUVEC) and human microvascular endothelial cells (HMEC-1) expressed PrPC mRNA. Flow cytometry confirmed PrPC expression on HMEC-1s and HUVECs (120900 +/- 15058 and 58327 +/- 4577 molecules PrPC/cell respectively), with no upregulation following cellular activation. Confocal immunofluorescence microscopy confirmed that HMEC-1s and HUVECs were positive for PrPC on the plasma membrane. Time-resolved dissociation-enhanced fluoroimmunoassay (DELFIA) analysis of cell culture medium demonstrated a slow constitutive release of soluble PrPC not associated with activation. In contrast to von Willebrand factor antigen, PrPC plasma levels in vivo decrease following desmopressin therapy in patients with von Willebrand disease. Measurement of PrPC plasma levels in patients with varying blood counts demonstrated no association between cell count and PrPC concentration. However, there was a higher level of PrPC in plasma from patients with end-stage renal failure. In conclusion, endothelial cells of both macrovascular and microvascular origin expressed high levels of PrPC which can be constitutively released into the cell culture medium.
British Journal of Haematology 01/2003; 119(3):863-73. · 4.94 Impact Factor
