Thromboembolic Disease – Critical Evaluation of Laboratory Investigation

1992 ◽  
Vol 68 (01) ◽  
pp. 007-013 ◽  
Author(s):  
Johan Malm ◽  
Martin Laurell ◽  
Inga Marie Nilsson ◽  
Björn Dahlbäck
Keyword(s):  
Plasminogen Activator ◽  
Laboratory Investigation ◽  
Patient Group ◽  
Vitamin K ◽  
Protein C ◽  
Protein S ◽  
Venous Occlusion ◽  
Thromboembolic Disease ◽  
Fibrinolytic System ◽  
Laboratory Evaluation

SummaryPrevious studies of patients with thromboembolic disease have revealed an association either with hereditary anticoagulant protein deficiencies or with defects in the fibrinolytic system. To obtain a more comprehensive picture and to investigate which analyses are useful in the evaluation of such patients, we have performed an extensive laboratory investigation in 439 individuals with thromboembolic disease. Anticoagulant protein deficiencies were found in 24 patients. Deficiencies of protein C (n = 10) and protein S (n = 9) were most common followed by deficiencies of antithrombin III (n = 3) and plasminogen (n = 2). Six of the nine protein S deficient patients demonstrated a selective deficiency of free protein S with normal total protein S concentrations. To diagnose protein C and S deficiencies among the 201 patients receiving oral vitamin K antagonists, the concentrations of protein C and S were compared with the mean concentration of several other vitamin K-dependent proteins. One protein C and three protein S deficiencies were identified among the treated patients. The number of protein C deficiencies found in this group was significantly lower than the number found among untreated patients. Although fewer protein S deficiencies were also identified among the treated patients, than in the untreated group, the difference was not statistically significant. The results suggest that protein C deficiencies went undetected in the treated group and that oral anticoagulant therapy should be discontinued before efforts to diagnose protein C deficiency are made. We found no cases with heparin cofactor II deficiency. Lupus anticoagulant was present in 10 patients. Evaluation of the fibrinolytic system revealed that the patient group had slightly lower mean euglobulin fibrinolytic activity (EFA) after venous occlusion than controls and a subgroup (approximately 15%) of patients with EFA below the level of the 5th percentile of controls, could be distinguished. Repeated analysis demonstrated a substantial individual day-to-day variation in both patients and controls and the combined EFA results did not clearly distinguish patients from controls. There was a significant negative correlation between EFA and plasminogen activator inhibitor (PAI) levels in both patients and controls and the patient group had significantly higher levels of PAI than the control group. In contrast, there was no difference between controls and patients in tissue plasminogen activator (tPA) release after venous occlusion and no correlation between EFA and tPA was observed. These results suggest that although a statistically significant difference between patients and controls in values of fibrinolytic parameters was found, an extensive laboratory evaluation of the fibrinolytic system in individual patients may not be warranted. The association between patients with thrombosis and deficiencies of anticoagulant proteins suggests that the investigation of individual patients should focus on these components.

APC Resistance and other Haemostatic Variables during Pregnancy and Puerperium

1999 ◽  
Vol 81 (04) ◽  
pp. 527-531 ◽  
Author(s):  
U. Kjellberg ◽  
N.-E. Andersson ◽  
S. Rosén ◽  
L. Tengborn ◽  
M. Hellgren
Keyword(s):  
Factor Viii ◽  
Plasminogen Activator ◽  
Protein C ◽  
Activated Protein C ◽  
Plasminogen Activator Inhibitor ◽  
Protein S ◽  
Reference Level ◽  
Soluble Fibrin ◽  
Prothrombin Fragment ◽  
D Dimer

SummaryForty-eight healthy pregnant women were studied prospectively and longitudinally. Blood sampling was performed at 10-15, 23-25, 32-34 and 38-40 weeks of gestation, within one week and at eight weeks postpartum. Classic and modified activated protein C ratio decreased as pregnancy progressed. In the third trimester 92% of the ratios measured with the classic test were above the lower reference level whereas all modified test ratios were normal. Slight activation of blood coagulation was shown with increased levels of prothrombin fragment 1+2, soluble fibrin and D-dimer. Fibrinogen, factor VIII and plasminogen activator inhibitor type 1 and type 2 increased. Protein S and tissue plasminogen activator activity decreased. Protein C remained unchanged. No correlation was found between the decrease in classic APC ratio and changes in factor VIII, fibrinogen, protein S, prothrombin fragment 1+2 or soluble fibrin, nor between the increase in soluble fibrin and changes in prothrombin fragment 1+2, fibrinogen and D-dimer.

Activated Protein C Increases Fibrin Clot Lysis by Neutralization of Plasminogen Activator Inhibitor No Evidence for a Cofactor Role of Protein S

1988 ◽  
Vol 60 (02) ◽  
pp. 328-333 ◽  
Author(s):  
N J de Fouw ◽  
Y F de Jong ◽  
F Haverkate ◽  
R M Bertina
Keyword(s):  
Plasminogen Activator ◽  
Protein C ◽  
Blood Platelets ◽  
Plasminogen Activator Inhibitor ◽  
Protein S ◽  
Tissue Type ◽  
Clot Lysis ◽  
Activator Inhibitor ◽  
Pai 1

summaryThe effect of purified human activated protein G (APC) on fibrinolysis was studied using a clot iysis system consisting of purified glu-plasminogen, tissue-type plasminogen activator, plasminogen activator inhibitor (released from endothelial cells or blood platelets), fibrinogen, 125T-fibrinogen and thrombin. All proteins were of human origin.In this system APC could increase fibrinolysis in a dose dependent way, without affecting fibrin formation or fibrin crosslinking. However, this profibrinolytic effect of APC could only be observed when plasminogen activator inhibitor (PAI-l) was present. The effect of APC was completely quenched by pretreatment of APC with anti-protein C IgG or di-isopropylfluorophosphate. Addition of the cofactors of APC:protein S, Ca2+-ions and phospholipid-alone or in combination did not enhance the profibrinolytic effect of APC. These observations indicate that human APC can accelerate in vitro clot lysis by the inactivation of PAI-1 activity. However, the neutralization of PAI-1 by APC is independent of the presence or absence of protein S, phospholipid and Ca2+-ions.

Protein S and C4b-Binding Protein: Components Involved in the Regulation of the Protein C Anticoagulant System

1991 ◽  
Vol 66 (01) ◽  
pp. 049-061 ◽  
Author(s):  
Björn Dahlbäck
Keyword(s):  
Vitamin K ◽  
Complement System ◽  
Protein C ◽  
Protein S ◽  
High Affinity ◽  
Anticoagulant System ◽  
Dependent Protein ◽  
The Complement System ◽  
Β Chain ◽  
Dependent Domain

SummaryThe protein C anticoagulant system provides important control of the blood coagulation cascade. The key protein is protein C, a vitamin K-dependent zymogen which is activated to a serine protease by the thrombin-thrombomodulin complex on endothelial cells. Activated protein C functions by degrading the phospholipid-bound coagulation factors Va and VIIIa. Protein S is a cofactor in these reactions. It is a vitamin K-dependent protein with multiple domains. From the N-terminal it contains a vitamin K-dependent domain, a thrombin-sensitive region, four EGF)epidermal growth factor (EGF)-like domains and a C-terminal region homologous to the androgen binding proteins. Three different types of post-translationally modified amino acid residues are found in protein S, 11 γ-carboxy glutamic acid residues in the vitamin K-dependent domain, a β-hydroxylated aspartic acid in the first EGF-like domain and a β-hydroxylated asparagine in each of the other three EGF-like domains. The EGF-like domains contain very high affinity calcium binding sites, and calcium plays a structural and stabilising role. The importance of the anticoagulant properties of protein S is illustrated by the high incidence of thrombo-embolic events in individuals with heterozygous deficiency. Anticoagulation may not be the sole function of protein S, since both in vivo and in vitro, it forms a high affinity non-covalent complex with one of the regulatory proteins in the complement system, the C4b-binding protein (C4BP). The complexed form of protein S has no APC cofactor function. C4BP is a high molecular weight multimeric protein with a unique octopus-like structure. It is composed of seven identical α-chains and one β-chain. The α-and β-chains are linked by disulphide bridges. The cDNA cloning of the β-chain showed the α- and β-chains to be homologous and of common evolutionary origin. Both subunits are composed of multiple 60 amino acid long repeats (short complement or consensus repeats, SCR) and their genes are located in close proximity on chromosome 1, band 1q32. Available experimental data suggest the β-chain to contain the single protein S binding site on C4BP, whereas each of the α-chains contains a binding site for the complement protein, C4b. As C4BP lacking the β-chain is unable to bind protein S, the β-chain is required for protein S binding, but not for the assembly of the α-chains during biosynthesis. Protein S has a high affinity for negatively charged phospholipid membranes, and is instrumental in binding C4BP to negatively charged phospholipid. This constitutes a novel mechanism for control of the complement system on phospholipid surfaces. Recent findings have shown circulating C4BP to be involved in yet another calcium-dependent protein-protein interaction with a protein known as the serum amyloid P-component (SAP). The binding sites on C4BP for protein S and SAP are independent. SAP, which is a normal constituent in plasma and in tissue, is a so-called pentraxin being composed of 5 non-covalently bound 25 kDa subunits. It is homologous to C reactive protein (CRP) but its function is not yet known. The specific high affinity interactions between protein S, C4BP and SAP suggest the regulation of blood coagulation and that of the complement system to be closely linked.

Laboratory Evaluation and Clinical Characteristics of 2,132 Consecutive Unselected Patients with Venous Thromboembolism – Results of the Spanish Multicentric Study on Thrombophilia (EMET*-Study)

1997 ◽  
Vol 77 (03) ◽  
pp. 444-451 ◽  
Author(s):  
José Mateo ◽  
Artur Oliver ◽  
Montserrat Borrell ◽  
Núria Sala ◽  
Jordi Fontcuberta ◽  
...  
Keyword(s):  
Venous Thrombosis ◽  
Odds Ratio ◽  
Protein C ◽  
Protein S ◽  
Laboratory Evaluation ◽  
Clinical Factors ◽  
Recurrent Thrombosis ◽  
Heparin Cofactor Ii ◽  
Crude Odds Ratio ◽  
History Of

SummaryPrevious studies on the prevalence of biological abnormalities causing venous thrombosis and the clinical characteristics of thrombotic patients are conflicting. We conducted a prospective study on 2,132 consecutive evaluable patients with venous thromboembolism to determine the prevalence of biological causes. Antithrombin, protein C, protein S, plasminogen and heparin cofactor-II deficiencies, dysfibrinoge-nemia, lupus anticoagulant and antiphospholipid antibodies were investigated. The risk of any of these alterations in patients with familial, recurrent, spontaneous or juvenile venous thrombosis was assessed. The overall prevalence of protein deficiencies was 12.85% (274/2,132) and antiphospholipid antibodies were found in 4.08% (87/2,132). Ten patients (0.47%) had antithrombin deficiency, 68 (3.19%) protein C deficiency, 155 (7.27%) protein S deficiency, 16 (0.75%) plasminogen deficiency, 8 (0.38%) heparin cofactor-II deficiency and 1 had dysfib-rinogenemia. Combined deficiencies were found in 16 cases (0.75%). A protein deficiency was found in 69 of 303 (22.8%) patients with a family history of thrombosis and in 205/1,829 (11.2%) without a history (crude odds ratio 2.34, 95% Cl 1.72-3.17); in 119/665 (17.9%) patients with thrombosis before the age of 45 and in 153/1,425 (10.7%) after the age of 45 (crude odds ratio 1.81, 95% Cl 1.40-2.35); in 103/616 (16.7%) with spontaneous thrombosis and in 171/1,516 (11.3%) with secondary thrombosis (crude odds ratio 1.58, 95% Cl 1.21-2.06); in 68/358 (19.0%) with recurrent thrombosis and in 206/1,774 (11.6%) with a single episode (crude odds ratio 1.78,95% Cl 1.32-2.41). Patients with combined clinical factors had a higher risk of carrying some deficiency. Biological causes of venous thrombosis can be identified in 16.93% of unselected patients. Family history of thrombosis, juvenile, spontaneous and recurrent thrombosis are the main clinical factors which enhance the risk of a deficiency. Laboratory evaluation of thrombotic patients is advisable, especially if some of these clinical factors are present.

scholarly journals The gene encoding vitamin K-dependent anticoagulant protein C is expressed in human male reproductive tissues.

1995 ◽  
Vol 43 (6) ◽  
pp. 563-570 ◽  
Author(s):  
X He ◽  
L Shen ◽  
A Bjartell ◽  
J Malm ◽  
H Lilja ◽  
...  
Keyword(s):  
Vitamin K ◽  
Leydig Cells ◽  
Protein C ◽  
Protein S ◽  
Northern Blotting ◽  
Human Testis ◽  
Post Translational Modification ◽  
Reproductive Tissues ◽  
Human Male ◽  
Dependent Protein

Protein C is a vitamin K-dependent protein circulating in plasma as a zymogen to an anticoagulant serine protease. After its activation, protein C cleaves and inactivates coagulation factors Va and VIIIa. Human protein C is synthesized in liver and undergoes extensive post-translational modification during its synthesis. Recently, the protein C inhibitor was demonstrated to be synthesized in several organs of the human male reproductive tract. Moreover, vitamin K-dependent protein S, which functions as a co-factor to activated protein C, was found to be synthesized in the Leydig cells of human testis. The aim of this study was to elucidate whether the protein C gene is also expressed in the male reproductive system. Specific immunostaining of protein C was found in Leydig cells of human testis, in the excretory epithelium of epididymis, and in some epithelial glands of the prostate, whereas no immunostaining was detected in seminal vesicles. Northern blotting and non-radioactive in situ hybridization demonstrated protein C mRNA in Leydig cells, in the excretory epithelium of epididymis, and in some of the epithelial glands of the prostate. The mRNA was distributed perinuclearly and the localization was in accordance with the specific immunostaining for protein C. The epithelium of epididymis was also found to contain both protein S mRNA and immunoreactivity. The demonstration of both protein C and protein S immunoreactivities, as well as their mRNAs, in male reproductive tissues suggests as yet unknown local functions for these proteins.

scholarly journals Vitamin K-Dependent Coagulation Factors That May be Responsible for Both Bleeding and Thrombosis (FII, FVII, and FIX)

2018 ◽  
Vol 24 (9_suppl) ◽  
pp. 42S-47S ◽  
Author(s):  
Antonio Girolami ◽  
Silvia Ferrari ◽  
Elisabetta Cosi ◽  
Claudia Santarossa ◽  
Maria Luigia Randi
Keyword(s):  
Venous Thrombosis ◽  
Vitamin K ◽  
Protein C ◽  
Protein S ◽  
Coagulation Factors ◽  
Bleeding Tendency ◽  
Clotting Factors ◽  
Protein Z ◽  
Clinical Observations

Vitamin K-dependent clotting factors are commonly divided into prohemorrhagic (FII, FVII, FIX, and FX) and antithrombotic (protein C and protein S). Furthermore, another protein (protein Z) does not seem strictly correlated with blood clotting. As a consequence of this assumption, vitamin K-dependent defects were considered as hemorrhagic or thrombotic disorders. Recent clinical observations, and especially, recent advances in molecular biology investigations, have demonstrated that this was incorrect. In 2009, it was demonstrated that the mutation Arg338Leu in exon 8 of FIX was associated with the appearance of a thrombophilic state and venous thrombosis. The defect was characterized by a 10-fold increased activity in FIX activity, while FIX antigen was only slightly increased (FIX Padua). On the other hand, it was noted on clinical grounds that the thrombosis, mainly venous, was present in about 2% to 3% of patients with FVII deficiency. It was subsequently demonstrated that 2 mutations in FVII, namely, Arg304Gln and Ala294Val, were particularly affected. Both these mutations are type 2 defects, namely, they show low activity but normal or near-normal FVII antigen. More recently, in 2011-2012, it was noted that prothrombin defects due to mutations of Arg596 to Leu, Gln, or Trp in exon 15 cause the appearance of a dysprothrombinemia that shows no bleeding tendency but instead a prothrombotic state with venous thrombosis. On the contrary, no abnormality of protein C or protein S has been shown to be associated with bleeding rather than with thrombosis. These studies have considerably widened the spectrum and significance of blood coagulation studies.

scholarly journals Thrombophilia And Arterial Ischemic Stroke

2017 ◽  
pp. 45
Author(s):  
A.A. Abrishamizadeh
Keyword(s):  
Ischemic Stroke ◽  
Vitamin K ◽  
Arterial Thrombosis ◽  
Protein C ◽  
Antithrombin Iii ◽  
Factor V Leiden ◽  
Protein S ◽  
Factor V ◽  
Factor V Leiden Mutation ◽  
C Protein

Ischemic stroke (IS) is a common cause of morbidity and mortality with significant socioeconomic impact especially when it affects young patients. Compared to the older adults, the incidence, risk factors, and etiology are distinctly different in younger IS. Hypercoagulable states are relatively more commonly detected in younger IS patients.Thrombophilic states are disorders of hemostatic mechanisms that result in a predisposition to thrombosis .Thrombophilia is an established cause of venous thrombosis. Therefore, it is tempting to assume that these disorders might have a similar relationship with arterial thrombosis. Despite this fact that 1-4 % of ischemic strokes are attributed to Thrombophillia, this   alone rarely causes arterial occlusions .Even in individuals with a positive thrombophilia screen and arterial thrombosis, the former might not be the primary etiological factor.Thrombophilic   disorders can be broadly divided into inherited or acquired conditions. Inherited thrombophilic states include deficiencies of natural anticoagulants such as protein C, protein S, and antithrombin III (AT III) deficiency, polymorphisms causing resistance to activated protein C(Factor V Leiden mutation), and disturbance in the clotting balance (prothrombin gene 20210G/A variant). Of all the inherited  thrombophilic disorders, Factor V Leiden mutation is perhaps the commonest cause. On the contrary, acquired thrombophilic disorders are more common and include conditions such as the antiphospholipid syndrome, associated with lupus anticoagulant and anticardiolipin antibodies.The more useful and practical approach of ordering various diagnostic tests for the uncommon thrombophilic states tests should be determined by a detailed clinical history, physical examination, imaging studies and evaluating whether an underlying hypercoagulable state appears more likely.The laboratory thrombophilia   screening should be comprehensive and avoid missing the coexisting defect and It is important that a diagnostic search protocol includes tests for both inherited and acquired thrombophilic disorders.Since the therapeutic approach (anticoagulation and thrombolytic therapy) determines the clinical outcomes, early diagnosis of the thrombophilic  disorders plays an important role. Furthermore, the timing of test performance of some of the  thrombophilic  defects (like protein C, protein S, antithrombin III and fibrinogen levels) is often critical since these proteins can behave as acute phase reactants and erroneously elevated levels of these factors may be observed in patients with acute thrombotic events. On the other hand, the plasma levels of vitamin K-dependent proteins (protein C, protein S and APC resistance) may not be reliable in patients taking vitamin K antagonists. Therefore, it is suggested that plasma-based assays for these disorders should be repeated3 to 6 months after the initial thrombotic episode to avoid false-positive results and avoid unnecessary prolonged   anticoagulation therapy. The assays for these disorders are recommended after discontinuation of oral anticoagulant treatment or heparin for at least 2 weeks.    

PROTEIN C, PROTEIN S AND THE FIBRINOLYTIC SYSTEM IN PATIENTS WITH A HISTORY OF THROMBOSIS

1987 ◽  
Author(s):  
J Malm ◽  
M Laurell ◽  
I M Nilsson ◽  
B Dahlbäck
Keyword(s):  
Plasminogen Activator ◽  
Fibrinolytic Activity ◽  
Protein C ◽  
Protein S ◽  
Protein S Deficiency ◽  
Functional Protein ◽  
Protein C Deficiency ◽  
S Deficiency ◽  
Tissue Plasminogen ◽  
History Of

Consecutive patients with a history of thrombo-embolic disease (n = 241, 109 males, 132 females, mean age 46 y), referred to the Coagulation Laboratory during an 18 month period, were analysed for defects in their coagulation and fibrinolytic systems. The diagnosis of thrombosis had been verified with phlebography and that of pulmonary embolus with scintigraphy or angiography. Retinal venous thrombosis was found in 15 of the patients. In 15 cases the thrombotic episodes occurred postoperatively, in 15 during pregnancy, in 12 during the postpartum period and in 20 during use of oral contraceptives. In the remaining cases no clinical riskfactors were identified.The concentration of protein C zymogen was measured with an immunoradiometric assay. Functional protein C was determined with a clotting inhibition assay. Protein C deficiency was found in 8 cases. Two of these had a functional protein C deficiency with normal zymogen levels. The concentration of total, as well as free (not in complex with C4b-binding protein), protein S was determined with a radioimmunoassay. Two cases of protein S deficiency were detected. Three patients with antithrombin III deficiency and two with plasminogen deficiency were found.The fibrinolytic activity after venous occlusion was analysed in 216 patients. Decreased levels were found in 32 %. The concentration of tissue plasminogen activator inhibitor (PAI) was measured in 110 patients and found to be increased in 65 % of the cases. In 99 patients both the fibrinolytic activity and the PAI concentration were measured. A combination of decreased fibrinolytic activity and increased levels of PAI was found in 44 cases. The concentration of tissue plasminogen activator antigen was decreased in 22 % of 105 cases analysed.Thus, in this material of patients with thrombo-embolic disease, abnormalities were found in 47 %. Defects in the fibrinolytic system were the most common findings. Protein C or protein S deficiency was diagnosed in less than 5 % of the cases.

THROMBOPHILIA:ITS CAUSES AND A ROUGH ESTIMATE OF ITS PREVALENCE

1987 ◽  
Author(s):  
E Briët ◽  
L Engesser ◽  
E J P Brommer ◽  
A W Broekmans ◽  
R M Bertina
Keyword(s):  
Plasminogen Activator ◽  
Protein C ◽  
Antithrombin Iii ◽  
Plasminogen Activator Inhibitor ◽  
Protein S ◽  
Factor Vii ◽  
Type I ◽  
Factor V ◽  
Protein C Deficiency ◽  
Familial Cases

Idiopathic venous thrombosis and embolism have gained widespread interest since the discovery that, deficiencies of antithrombin III, protein C, and protein S are associated with familial venous thrombophilia. The purpose of our study was to obtain an estimate of the prevalence of this syndrome and to establish the etiology in as many cases as possible.We collaborated with specialists from 37 Dutch hospitals, covering about 10% of the Dutch population. A history as well as blood samples were obtained from 113 unrelated cases with familial thrombophilia and from 90 isolated cases. Assuming that each proband in a family with thrombophilia has an average of four affected relatives, a rough estimate of the prevalence of familial thrombophilia in The Netherlands is 40 cases per 100.000. The prevalence of non-familial thrombophilia is probably lower.In 35 out of the 113 familial cases we established a diagnosis of hereditary antithrombin III deficiency (n=5), protein C deficiency (type I: n=9; type II: n=4), protein S deficiency (n=15) and dysfibrinogenemia (n=2). In 36 cases we found no abnormality at all and in the remaining 42 cases abnormalities were found in one or more of the following: heparin cofactor II, factor V, factor VII, factor VIII, von Willebrand factor, plasminogen, tissue plasminogen activator, plasminogen activator inhibitor, alpha 2 antiplasmin and histidine rich glycoprotein. In most of these cases, however, the hereditary nature of the abnormalities could not be demonstrated and the causal relationships remain to be established.In the 90 isolated cases, we diagnosed hereditary deficiencies of anti thrombin III, protein C and protein S each in one case and a lupus anticoagulant in two cases. In 54 cases no abnormality was found and in the remaining 31 cases various abnormalities were found in one or more of the proteins mentioned above.We conclude that the syndrome of thrombophilia is not rare but its true prevalence needs to be established by more rigorous means. An etiological diagnosis can be made with confidence in only one third of the familial cases and in less than 10 percent of the isolated cases.

REDUCED TISSUE PLASMINOGEN ACTIVATOR RELEASE AND NORMAL PLASMINOGEN ACTIVATOR INHIBITOR LEVEL IN A FAMILY WITH RECURRENT VENOUS THROMBOSES

1987 ◽  
Author(s):  
J Petäjä ◽  
G Myllylä ◽  
V Rasi ◽  
E Vahtera
Keyword(s):  
Plasminogen Activator ◽  
Tissue Plasminogen Activator ◽  
Plasminogen Activator Inhibitor ◽  
Protein S ◽  
Venous Occlusion ◽  
C Protein ◽  
Tissue Plasminogen ◽  
Inhibitor Level ◽  
Fast Acting ◽  
Activator Inhibitor

We have studied the fibrinolytic system in one asymptomatic and six symptomatic members of a family with recurrent DVTs in three generations. Tissue plasminogen activator activity (TPA) and fast acting inhibitor of TPA (PAI) were determined using chromogenic substrate and TPA antigen with ELISA. Measurements were made at rest and after 10 and 20 minutes of venous occlusion (VO). 17 healthy subjects served as controls. The mean TPA in the seven family members was significantly lower than in controls at 10 and 20 min VO (p< 0.01).TPA was below the lowest value of controls (<1.7 U/ml) in five of the six patients with DVT at 10 min VO and remained below the range of controls in three at 20 min VO (<3.3 U/ml). The lowered TPA activity was associated with impaired release of TPA antigen (mean level at 10 min VO 12.A ng/ml, controls 19.5 ng/ml, p<0.05; at 20 min VO 18.2 ng/ml, controls 43.2 ng/ml, p<0.01). Four .patients with and one without DVT had TPA antigen below the lowest level of controls at 10 and/or 20 min VO. The level of'PAI at rest was normal in all cases (from 0.6 to 1.7 U/ml, controls from 0 to 3.7 U/ml). In accordance with low release of TPA antigen PAI was consumed less during VO in patients than in controls (mean level at 20 min VO 0.9 U/ml, controls 0.4 U/ml, p<0.05). The levels of antithrombin III, protein C, protein S, plasminogen, fibrinogen, F V, F VIII:C, vWf:Ag, fibrinopeptide A and beta-thromboglobulin were normal . Circulating anticoagulant was not found. It is concluded that impaired release of TPA, independent of PAI, is associated with DVT in this family. The pattern of inheritance suggested autosomal dominant trait.

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