F. E. Preston

Inhibition of activated protein C and its cofactor protein S by antiphospholipid antibodies

Summary. We have investigated the effects of purified IgG fractions from plasma containing the lupus anticoagulant (LAC) and/or IgG anticardiolipin antibody (ACA) on the degradation of factor Va by an activated protein C‐protein S complex. Plasma samples from 10 patients were studied. LAC was detected by a Russells Viper venom technique. ACA was determined by ELISA. IgG fractions were obtained from each plasma sample by protein A‐Sepharose fractionation. This fraction was shown to exhibit ACAILAC activity. Using purified activated protein C (APC), protein S and phosphati‐dylserine/phosphatidylcholine, factor Va degradation was assessed in the presence and absence of IgG fractions from LAC/ACA containing plasmas. After 2 min incubation the mean factor Va degradation by APC and protein S in the presence of IgG LAC/ACA fractions was 14% compared with 52% with normal IgG. A similar effect was seen when phospholipid was substituted by washed freeze‐thawed platelets. Experiments employing varying concentrations of protein S and phospholipid revealed marked differences in respect of the inhibitory specificity of the different antiphospholipid antibodies. These results indicate that antiphospholipid antibodies have an inhibitory effect on the activated protein C/protein S complex and provide some explanation for a relationship between antiphospholipid antibodies and thrombosis.

Rapid reversal of oral anticoagulation with warfarin by a prothrombin complex concentrate (Beriplex): efficacy and safety in 42 patients

Summary.  Beriplex, a prothrombin complex concentrate (PCC), was administered to 42 patients requiring immediate reversal of their oral anticoagulant therapy. The dose administered was determined using the pretreatment International Normalized Ratio (INR). Blood samples were obtained before treatment and at 20, 60 and 120 min after treatment. The following investigations were performed on all samples – INR, clotting factors II, VII, IX and X, coagulation inhibitors protein C (PC) and antithrombin (AT), and other markers of disseminated intravascular coagulation, plasma fibrinogen, d‐dimer and platelet count. Immediate reversal of the INR, the vitamin K‐dependent clotting factors and PC was achieved in virtually all patients. Reduced AT levels were present in 18 patients before treatment. Further slight AT reductions occurred in four patients, but other associated abnormalities of haemostasis were observed in only one of the four patients. One patient with severe peripheral vascular disease, sepsis and renal and cardiac failure died of a thrombotic stroke following leg amputation, 48 h after receiving Beriplex. No other arterial and no venous thromboembolic events occurred within 7 d of treatment. Beriplex is effective in rapidly reversing the anticoagulant effects of warfarin, including PC deficiency, without inducing coagulation activation. Caution should continue to be exercised in the use of these products in patients with disseminated intravascular coagulation, sepsis or liver disease.

The natural history of chronic hepatitis C in haemophiliacs

Most haemophiliacs treated with non‐virally‐inactivated clotting factor concentrates have been infected with hepatitis C virus (HCV). We have studied the natural history of chronic HCV infection by following all 138 HCV‐positive patients from our centre for periods of up to 28 years. As well as the clinical and biochemical characteristics, we studied 116 liver samples from 63 patients obtained at elective biopsy (n=103) or autopsy (n=13). 36 (26%) of the patients were HIV positive, and three were chronic carriers of hepatitis B. Evidence of previous exposure to hepatitis A and B was found in 37.2% and 48.1% respectively. Raised transaminase levels were found in 82.6% of patients. 11 of 15 patients with normal transaminases tested by PCR for HCV RNA were positive, indicating that most patients, even in this group, have chronic hepatitis C infection. Cirrhosis was diagnosed by liver histology in 19 patients, and nine patients developed liver failure. The incidence of cirrhosis rose rapidly 15 years after HCV infection to 15.6 per 1000 person‐years. Multivariate analysis showed that HIV status, length of time since HCV infection and age at HCV infection were independently associated with both the development of cirrhosis and liver failure. Two patients developed hepatocellular carcinoma; one of these was exposed only to a single batch of FVIII concentrate 11 years earlier. Chronic hepatitis C is increasingly recognized as a major cause for morbidity and mortality in haemophiliacs, especially those who are HIV positive and who were infected at an older age.

Risk of a first venous thrombotic event in carriers of a familial thrombophilic defect. The European Prospective Cohort on Thrombophilia (EPCOT)

Summary.  Background: Reliable risk estimates for venous thrombosis in families with inherited thrombophilia are scarce but necessary for determining optimal screening and treatment policies. Objectives: In the present analysis, we determined the risk of a first venous thrombotic event in carriers of a thrombophilic defect (i.e. antithrombin‐, protein C‐ or protein S deficiency, or factor V Leiden). Patients and methods: The asymptomatic carriers had been tested prior to this study in nine European thrombosis centers because of a symptomatic carrier in the family, and were followed prospectively for 5.7 years on average between March 1994 and January 2001. Annually, data were recorded on the occurrence of risk situations for venous thrombosis and events (e.g. venous thrombosis, death). Results: Twenty‐six of the 575 asymptomatic carriers (4.5%) and seven of the 1118 controls (0.6%) experienced a first deep venous thrombosis or pulmonary embolism during follow‐up. Of these events, 58% occurred spontaneously in the carriers compared with 43% in the controls. The incidence of first events was 0.8% per year (95% CI 0.5–1.2) in the carriers compared with 0.1% per year (95% CI 0.0–0.2) in the controls. The highest incidence was associated with antithrombin deficiency or combined defects, and the lowest incidence with factor V Leiden. Conclusions: The incidence of venous events in asymptomatic individuals from thrombophilic families does not exceed the risk of bleeding associated with long‐term anticoagulant treatment in the literature (1–3%).

Essential thrombocythaemia and peripheral gangrene.

Six patients are described in whom gangrene of one or more toes occurred as the presenting feature of essential thrombocythaemia. Spontaneous platelet aggregation was observed in platelet-rich plasma from four patients and platelet aggregation after the addition of adenosine diphosphate and collagen was highly abnormal in samples from all six. All of the patients described dramatic relief of pain within six hours of ingestion of aspirin and this coincided with disappearance of the spontaneous platelet aggregation and collagen-induced platelet aggregation. Treatment with phosphorus-32 corrected the platelet count and there were no further recurrences of peripheral vascular disease. Platelet function tests performed at the time all gave normal results. It is concluded that essential thrombocythaemia is an important and treatable cause of peripheral vascular disease.

Plasma D-dimer levels and their relationship to serum fibrinogen/fibrin degradation products in hypercoagulable states.

Plasma D‐dimer was measured and compared with serum fibrinogen/fibrin degradation product levels (FDPs) in patients with disseminated intravascular coagulation (DIC) and other conditions associated with a hypercoagulable state. D‐dimer (N<200 ng/ml) was elevated in all 43 patients with DIC, in 48 of 59 patients with liver disease, in 22 of 27 patients with acute leukaemia at presentation, in 17 of 23 patients with malignant disease, in 29 of 39 women in the third trimester of a complicated pregnancy, in 17 of 18 patients with deep venous thrombosis and in only four of 27 patients with acute myocardial infarction. There was a significant correlation between plasma D‐dimer and serum FDP levels (P<0.01) as follows; DIC: r =r=0.58, liver disease: r=0.57, acute leukaemia: r=0.84, malignancy: r=0.87. The frequent elevation of D‐dimer observed in liver disease, acute leukaemia, malignancy and complicated pregnancy indicates that a hypercoagulable state is a common occurrence in these conditions although in liver disease elevated levels resulting from a failure of normal clearance mechanisms cannot be excluded. The close relationship between D‐dimer and FDP levels suggests that serum FDPs predominantly arise from the interaction of plasmin with crosslinked fibrin rather than with fibrinogen in the conditions in which these were compared.

HYPOTHYROIDISM AS A CAUSE OF ACQUIRED VON WDLLEBRAND'S DISEASE

Three patients with bleeding tendency who met the criteria for type 1 von Willebrands disease are described. In two patients, hypothyroidism was suspected and confirmed at presentation, and in the third hypothyroidism became apparent 4 years later. In all three, the history and clinical course after treatment with thyroxine indicated acquired von Willebrands disease secondary to hypothyroidism. The possibility of hypothyroidism should be considered in patients presenting with von Willebrands disease.

PLATELET ABNORMALITIES IN DIABETIC PERIPHERAL NEUROPATHY

Abnormal platelet function has been demonstrated in 20 patients with diabetic peripheral neuropathy. The results are compared to those obtained from 19 matched diabetic patients with no clinical evidence of complications and 20 matched normal control subjects. Platelets from patients with diabetic neuropathy showed an increased sensitivity to the aggregating agents adenosine diphosphate and adrenaline. Spontaneous platelet aggregation was demonstrated in both groups of diabetic patients.

Familial thrombophilia and lifetime risk of venous thrombosis

Summary  Background : We started a large multicenter prospective follow‐up study to provide reliable risk estimates of venous thrombosis in families with various thrombophilic defects.

Hereditary thrombophilia and fetal loss: a prospective follow-up study

Summary.  Background: As the placental vessels are dependent on the normal balance of procoagulant and anticoagulant mechanisms, inherited thrombophilia may be associated with fetal loss. Objectives: We performed a prospective study to investigate the relation between inherited thrombophilia and fetal loss, and the influence of thromboprophylaxis on pregnancy outcome. Patients and methods: Women were enrolled in the European Prospective Cohort on Thrombophilia (EPCOT). These included women with factor (F)V Leiden or a deficiency of antithrombin, protein C or protein S. Controls were partners or acquaintances of thrombophilic individuals. A total of 191 women (131 with thrombophilia, 60 controls) had a pregnancy outcome during prospective follow‐up. Risk of fetal loss and effect of thromboprophylaxis were estimated by frequency calculation and Cox regression modelling. Results: The risk of fetal loss appeared slightly increased in women with thrombophilia without a previous history of fetal loss who did not use any anticoagulants during pregnancy (7/39 vs. 7/51; relative risk 1.4; 95% confidence interval 0.4, 4.7). Per type of defect the relative risk varied only minimally from 1.4 for FV Leiden to 1.6 for antithrombin deficiency compared with control women. Prophylactic anticoagulant treatment during pregnancy in 83 women with thrombophilia differed greatly in type, dose and duration, precluding solid conclusions on the effect of thromboprophylaxis on fetal loss. No clear benefit of anticoagulant prophylaxis was apparent. Conclusions: Women with thrombophilia appear to have an increased risk of fetal loss, although the likelihood of a positive outcome is high in both women with thrombophilia and in controls.