Incidence and clinical characteristics of hereditary disorders associated with venous thrombosis

Outcome Analysis for Treatment in 100 Patients with Deep Vein Thrombosis

The treatment of acute deep vein thrombosis has been the subject of much research aimed at delineat ing the safest and most effective approach to diagnosis and treatment. Studies regarding long-term treatment have been limited by the narrow scope of laboratory and clinical analyses of many patients. In this study of 100 patients with a history of deep vein thrombosis, treated on an outpatient basis by a diverse group of clinicians, follow-up data were retrieved in order to determine the outcomes of various approaches to acute and long-term care. Among individuals followed for > 1 year, in only two patients (2%) was death attributable to a thrombotic event related to the etiology of the first episode of deep vein thrombosis. Most deceased patients succumbed to unrelated causes (11%). Among the 77 survivors, most (52%) received long-term antiplatelet therapy. All individ uals with a plasma coagulation defect, whether inherited or acquired, received anticoagulation with either heparin or warfarin. Since the long-term clinical outcome of most patients with deep vein thrombosis is dependent upon the underlying factor predisposing to thrombosis, the most important treatment decision is to select the therapy most likely to provide benefit without causing hemorrhage. An tiplatelet therapy, heparin, or warfarin may be chosen as appropriate for the individual patient.

Syndromes of Thrombosis and Hypercoagulability: Congenital and Acquired Thrombophilias

This article stresses the common hereditary and acquired blood protein defects associated with thrombosis. The most common of the hereditary defects apear to be APC-R, SPS, antithrombin, protein C, and protein S deficiency, and the most common acquired defects are anticardiolipin antibodies and the lupus anticoagulant (antiphospholipid antibodies). Therefore, these are the defects that should first be looked for in an individual with unexplained thrombosis. If these more common defects are not found, then the rarer defects including HC II, plasminogen or TPA deficiency, dysfibrinogenemia, el evated PAI-1 and hyperhomocysteinemia should be sought. The importance of finding these defects has significant impli cations for therapy of the individual patient and for institutions of family studies to identify, inform, and possibly treat others at risk. It is expected that as knowledge of hemostasis expands, more hereditary and acquired defects, such as elevated lipopro tein (a) or defects of extrinsic (tissue factor) pathway inhibitor (EPI, TFPI), may be associated with enhanced risks of throm bosis. Finally, it must be recalled that a diagnosis of thrombo sis, like that of anemia, is only a generic and partial diagnosis; just as in the anemic patient, the etiology must be clearly de fined. Only in this manner can cost-effective and appropriate therapy for both primary treatment and secondary prevention be designed. In addition, the demonstration of a hereditary defect will allow primary prevention in afflicted family mem bers by allowing the choice of appropriate therapy.

Different Anticoagulant Response to Activated Protein C (APC test) and to Agkistrodon Contortix Venom (ACV test) in a Family with FV-R506Q Substitution

To identify the defect(s) responsible for the thrombotic condition affecting a 55-year-old male and his family, we have utilized a new methodological approach (ProC Global®, Istituto Behring, Milan, Italy) to screen the global anticoagulant activity of the protein C pathway, a defect that accounts for the majority of inherited thrombophilias. The test is based on the activation of endogenous protein C in plasma by Protac®, derived from Agkistrodon contortix snake venom (ACV test). Nineteen members of the family were investigated, 11 showed low responsiveness to ACV (normalized ACV ratios < 0.66; normal > 1. 12); in these individuals specific assays of protein C (PC) and protein S (PS) levels and normalized activated protein C ratios (n-APC-r) were performed. A second test evaluating response to APC, using the classic commercial APC test (n-APC-r 1), detected only 10 subjects with abnormal responses : the propositus and two members of the family with n-APC-r 1 values < 0.54, indicating the homozygous state for the R506Q factor V gene mutation, and seven with values ranging 0.69-0.83, consistent with the heterozygous condition (normal > 0.85). Although only ten subjects presented with low n-APC-r 1 values, DNA analysis, in agreement with the ACV test, detected 11 individual with factor V-R506Q substitution (two homozygotes and nine heterozygotes). Thus the classical APC test failed to identify the APC resistance phenotype in two heterozygous subjects whose values were clearly normal (1.05) in the first case and homozygous (0.53) in the second. The ACV test, however, and the modified APC test with test plasma 1/5 diluted in factor V-deficient plasma (n-APC-r 2) completely matched the DNA analysis. A phenotype/genotype correlation was observed in dilutions higher than 1/3 test plasma factor V-deficient plasma. The presence of unknown mechanisms that influence plasma response to exogenous preformed APC (normal at high factor V-deficient plasma dilutions) but not endogenous ACV activated PC was suspected. The suspected low levels of proteins C and S found in several R506Q members of the family were excluded by reassaying the anticoagulant activities at higher plasma dilution ; this supports the known influence of factor V Leiden on functional PC and PS clotting activity. We conclude that the ACV test is appropriate to evaluate the APC resistance condition, but for a firm diagnosis DNA analysis together with the modified APC test are strongly advised even in the presence of unquestionable APC-r values. Key Words: APC resistance-Factor V Leiden-APC test-ACV test-Diagnosis-Inherited thrombophilia.

Deep venous thrombosis following different isolated lower extremity fractures: what is known about prevalences, locations, risk factors and prophylaxis?

INTRODUCTION

Deep venous thrombosis (DVT) offers a high risk of morbidity and mortality, especially in case of pulmonary embolism. Precise data as to DVT after isolated lower extremity fractures (ILEFs) are rare. Even organizations like the American Academy of Orthopaedic Surgeons or the American College of Chest Physicians do not state exact recommendations as to optimal DVT prophylaxis (ppx) after ILEFs.

PREVALENCE

The incidence of DVT ranges from 5 to 86 % depending on the fracture whereas femur fractures offer the highest risk for clotting. The incidence seems to decrease in more distal fractures.

LOCATION

The risk to develop proximal clots is likely low, however, especially these are feared by surgeons. DVT can occur in both the injured and uninjured leg with a trend for higher incidences in the injured leg.

RISK FACTORS

Risk factors for DVT after ILEF seem to be similar to risk factors for DVT development after orthopaedic surgery and in general. Risk factors caused by surgeons are the use of a tourniquet, prolonged operative time and a delay from injury to surgery.

PROPHYLAXIS

Low molecular weight heparin is favoured by many authors, however, warfarin and acetylsalicylic acid are also used. Clear recommendations are still missing.

CONCLUSION

The rate of morbidity caused by DVT after ILEF is poorly understood so far. Exact data on prevalences are missing and optimal DVT prophylaxis still has to be defined.

Activated Protein C Resistance and Factor V Leiden in Mexico

A common cause of hereditary thrombophilia is activated protein C resistance (APCR), and most cases result from factor V Leiden mutation. An APCR phenotype without association with factor V Leiden has been described. This transversal, observational, nonrandomized study evaluated these 2 phenomena in healthy indigenous and mestizo Mexican subjects (n = 4345), including 600 Mexican natives. No indigenous subjects had APCR, but 82 mestizo subjects did. After retesting, 50 subjects had a negative test. The remaining 32 subjects had factor V Leiden, giving a 0.85% prevalence of factor V Leiden in the mestizo Mexican population. Only 31% of APCR carriers had factor V Leiden. These results show a very low prevalence of APCR and factor V Leiden in Mexico. Except for factor V Leiden, there are no other mutations in the factor V gene responsible for the APCR phenotype. Acquired APCR is nearly twice as prevalent as the inherited variant.

Efficacy of family history in determining thrombophilia risk

STUDY OBJECTIVE

This retrospective study sought to examine the importance of family history of cardiovascular disease (CVD) or venous thromboembolism (VTE) in predicting risk for an inherited thrombophilia.

DESIGN/METHODS

A cohort of 88 adolescent females who had a thrombophilia panel in the last three years was identified for this retrospective chart review. Family history data of CVD or VTE were collected in addition to laboratory results from the thrombophilia screen.

SETTING

Adolescent patients who had a thrombophilia screen within the last three years at University OB-GYN Associates, Louisville, KY.

RESULTS

Within the cohort (n=88), 21% of patients were found to have a documented thrombophilia. At least 47% of individuals diagnosed with thrombophilia had more than one screening abnormality. A family history of VTE was noted to have a positive predictive value (PPV) of 40% and a negative predictive value (NPV) of 88% for detection of thrombophilia. Patients with a family history of CVD alone carried a PPV of 24% and NPV of 100%. Finally, among individuals with both family history risk factors, PPV was strengthened at 52% while NPV remained unchanged.

CONCLUSIONS

Within the last decade, inherited thrombophilias have gained more clinical interest. While thrombophilia disease prevalence data is available for the adult population, there remains a paucity of data in adolescents. Our results reinforce the importance for screening adolescent females, prior to contraceptive administration, if family history risk factors exist.

Evidence-based risk factors for postoperative deep vein thrombosis

BACKGROUND

Deep vein thrombosis (DVT) is a common postoperative complication that is associated with significant morbidity and mortality. Thromboprophylaxis has been shown to be underused. In the absence of prophylaxis, rates as high as 50% have been reported following orthopaedic surgery, and 25% following general surgery. Many risk factors have been suggested but there is often little evidence to support these claims.

METHODS

A systematic review was performed to determine the evidence base behind each suggested risk factor, and, where sufficient data were available, a random-effects meta-analysis was performed.

RESULTS

There is evidence to support a significant association between increased age, obesity, a past history of thromboembolism, varicose veins, the oral contraceptive pill, malignancy, Factor V Leiden gene mutation, general anaesthesia and orthopaedic surgery, with higher rates of postoperative DVT, although there remain some variables within the study designs that may lead to overestimation of effect. There is no evidence to support the suggested risk factors of hormone replacement therapy, gender, ethnicity or race, chemotherapy, other thrombophilias, cardiovascular factors, smoking and blood type.

CONCLUSIONS

An accurate knowledge of evidence-based risk factors is important in predicting and preventing postoperative DVT, and can be incorporated into a decision support system for appropriate thromboprophylaxis use.

Estudio prospectivo de los factores de riesgo y las características clínicas de la enfermedad tromboembólica en pacientes jóvenes

BACKGROUND AND OBJECTIVE

We aimed to determine the risk factors of thromboembolic disease in young patients and to study the clinical characteristics according to the etiology.

PATIENTS AND METHOD

A prospective study of 100 patients under 50 years who were not affected by neoplasias or chronic diseases and who required hospitalization due to thromboembolic disease. The morphological diagnosis was performed by eco-Doppler, flebography, lung gammagraphy or CT scan. Risk factors assessed were antithrombin, protein C and S deficiency, presence of factor V Leiden, prothrombin G20210A, hyperhomocisteinemia, increased PAI-I, increased factor VIII, and presence of antiphospholipid antibodies (APAs). Acquired factors were also evaluated.

RESULTS

In 87% of patients, a venous thrombosis was observed in lower limbs. 37% of patients had congenital risk factors and 19% had APAs, whereas in the remaining patients only acquired factors were demonstrated. Most frequent congenital factors were factor V Leiden, pothrombin G20210A, and protein C and S deficiency. Most patients presented several risk factors. A family thrombotic history was significantly more frequent in the group with congenital risk factors.

CONCLUSIONS

In 56% of young patients with thromboembolic disease, a congenital etiology or APAs are identified. In these patients the number of acquired factors needed to trigger thrombosis is fewer than in patients in whom a cause is not identified.

Risk factors for venous thromboembolism

Until the 1990s, venous thromboembolism (VTE) was viewed primarily as a complication of hospitalization for major surgery (or associated with the late stage of terminal illness). However, recent trials in patients hospitalized with a wide variety of acute medical illnesses have demonstrated a risk of VTE in medical patients comparable with that seen after major general surgery. In addition, epidemiologic studies have shown that between one quarter and one half of all clinically recognized symptomatic VTEs occur in individuals who are neither hospitalized nor recovering from a major illness. This expanding understanding of the population at risk challenges physicians to carefully examine risk factors for VTE to identify high-risk patients who could benefit from prophylaxis. Factors sufficient by themselves to prompt physicians to consider VTE prophylaxis include major surgery, multiple trauma, hip fracture, or lower extremity paralysis because of spinal cord injury. Additional risk factors, such as previous VTE, increasing age, cardiac or respiratory failure, prolonged immobility, presence of central venous lines, estrogens, and a wide variety of inherited and acquired hematological conditions contribute to an increased risk for VTE. These predisposing factors are seldom sufficient by themselves to justify the use of prophylaxis. Nevertheless, individual risk factors, or combinations thereof, can have important implications for the type and duration of appropriate prophylaxis and should be carefully reviewed to assess the overall risk of VTE in each patient.

Prothrombin G20210A mutation, antithrombin, heparin cofactor II, protein C, and protein S defects

These defects are not as common as factor V Leiden, but they are more common than many other hereditary procoagulant defects. The incidence of the prothrombin gene (G20210A) mutation is not yet known with certainty, but it may approach or even exceed that of factor V Leiden. These defects also seem less common than hereditary sticky platelet syndrome; however, they are all common enough that they always should be considered in any individual with unexplained thrombosis and should be part of the work-up for patients with thrombotic disorders. Of the defects discussed herein, prothrombin G20210A mutation seems, thus far, to be more common than AT, protein C, protein S, or HC-II defects. Assessment of prothrombin gene mutation should be part of the primary evaluation of patients with unexplained thrombosis.

Laboratory issues in diagnosing abnormalities of protein C, thrombomodulin, and endothelial cell protein C receptor

OBJECTIVE

To review the current understanding of the pathophysiology of protein C deficiency and its role in congenital thrombophilia. Recommendations for diagnostic testing for protein C function and concentration, derived from the medical literature and consensus opinions of recognized experts in the field, are included, specifying whom, how, and when to test. The role of related proteins, such as thrombomodulin and endothelial protein C receptor, is also reviewed. Data Sources.-Review of the published medical literature.

DATA EXTRACTION AND SYNTHESIS

A summary of the medical literature and proposed testing recommendations were prepared and presented at the College of American Pathologists Conference XXXVI: Diagnostic Issues in Thrombophilia. After discussion at the conference, consensus recommendations presented in this manuscript were accepted after a two-thirds majority vote by the participants.

CONCLUSIONS

Protein C deficiency is an uncommon genetic abnormality that may be a contributing cause of thrombophilia, often in conjunction with other genetic or acquired risk factors. When assay of protein C plasma levels is included in the laboratory evaluation of thrombophilia, a functional amidolytic protein C assay should be used for initial testing. The diagnosis of protein C deficiency should be established only after other acquired causes of protein C deficiency are excluded. A low protein C level should be confirmed with a subsequent assay on a new specimen. Antigenic protein C assays may be of benefit in subclassification of the type of protein C deficiency. The role of thrombomodulin and endothelial cell protein C receptor in thrombosis has yet to be clearly established, and diagnostic testing is not recommended at this time.

Plasminogen and tissue-type plasminogen activator deficiency as risk factors for thromboembolic disease

OBJECTIVE

To review the published evidence for an association between a deficiency of plasminogen or tissue-type plasminogen activator (tPA) and the risk of thrombosis.

DATA SOURCES

Review of the medical literature, with an emphasis on the last 10 years.

DATA EXTRACTION AND SYNTHESIS

After an initial assessment of the literature, including review of clinical study design and laboratory methods, a draft manuscript summarizing the findings was prepared and circulated to participants in the College of American Pathologists Conference on Diagnostic Issues in Thrombophilia. The key findings and each recommendation were presented for discussion at the conference. Recommendations were accepted if a consensus of the 27 experts attending the conference was reached. The results of the discussion were used to revise the manuscript into its final form.

CONCLUSIONS

The consensus of the conference was that routine laboratory assessment of plasminogen and tPA concentration in patients with thrombophilia is not warranted at this time. Analysis of plasminogen and tPA gene alterations in patients with thrombophilia is also not warranted at this time. Determination of plasminogen concentration should be performed in patients suspected of having ligneous conjunctivitis.

Antithrombin deficiency: issues in laboratory diagnosis

OBJECTIVE

To review the current understanding of the pathophysiology of antithrombin deficiency and its role in congenital thrombophilia. Recommendations for diagnostic testing of antithrombin function and concentration, derived from the medical literature and consensus opinions of recognized experts in the field, are included. These recommendations specify whom, how, and when to test.

DATA SOURCES

Review of the published medical literature.

DATA EXTRACTION AND SYNTHESIS

A summary of the medical literature and proposed testing recommendations were prepared and presented at the College of American Pathologists Conference XXXVI: Diagnostic Issues in Thrombophilia. After discussion at the conference, consensus recommendations presented in this article were accepted after a two-thirds majority vote by the participants.

CONCLUSIONS

Antithrombin deficiency is an infrequent genetic abnormality that may be a significant contributing cause of thrombophilia. Antithrombin deficiency also may be observed in conjunction with other genetic or acquired risk factors. Assay of antithrombin plasma levels is appropriate in the laboratory evaluation of individuals with thrombophilia, preferably using a functional, amidolytic antithrombin assay. The diagnosis of antithrombin deficiency should be established only after other acquired causes of antithrombin deficiency, such as liver disease, consumptive coagulopathy, or heparin therapy, are excluded. A low antithrombin level should be confirmed with a subsequent assay on a fresh specimen, and family studies may be helpful to establish the diagnosis. Antigenic antithrombin assays may be of benefit in subclassification of the type of antithrombin deficiency and to confirm the decreased antithrombin level in patients with type I deficiency.

Risk factors for thromboembolism in teens: when should I test?

The discoveries of the factor V Leiden mutation and the prothrombin gene variant 20210 in the last decade have markedly contributed to the understanding of the molecular pathophysiology of inherited risk factors for thrombophilia. Population studies in the adult literature have shown that although the overall prevalence of these defects is low, affected individuals are at increased risk of thrombosis particularly if acquired risk factors for thrombosis are also present. The use of combined hormonal oral contraceptive pills is a well-known acquired risk factor, and recent studies have shown significant increased risk of thrombosis for women who carry the factor V Leiden mutation and use oral contraceptive pills. Despite this significant increased risk, mass screening of asymptomatic women for factor V Leiden prior to prescribing oral contraceptive pills is not a cost-effective use of health care dollars and could result in unnecessarily preventing many women from the contraceptive and noncontraceptive benefits of this medication. Instead, clinicians can use thoughtful screening questions to identify potentially high-risk patients for thrombophilia and consider testing for inherited risk factors on a case-specific basis.

Acute renal vein thrombosis, oral contraceptive use, and hyperhomocysteinemia

Oral contraceptive use and hyperhomocysteinemia are considered to be relatively weak risk factors for venous thromboembolism. We report a case of acute renal vein thrombosis, a rare and aggressive form of thromboembolism, that occurred in a 21-year-old woman taking oral contraceptives, who was subsequently found to have marked hyperhomocysteinemia. This case suggests that the oral contraceptive and hyperhomocysteinemia may interact in a synergistic manner in the pathogenesis of thrombosis. In oral contraceptive users who develop venous thrombosis in the absence of other risk factors, clinicians should consider investigations for an underlying prothrombotic biochemical disorder.

Frequency of protein S deficiency in general Japanese population

We measured protein S (PS) activity in a large group of Japanese subjects to study the frequency of PS deficiency. The study group comprised 213 men, ages 18-58 years, and 179 women, ages 18-60 years. PS activity in the total 392 subjects was 58-135% (mean +/- 2 SD), 65-135% in the men and 54-120% in the women. The men showed significantly higher levels of PS activity than the women (p<0.001). We identified 8 subjects (4 men and 4 women) in whom PS activity was lower than the mean-2SD for men and women, respectively. Moreover, we examined the classifications of PS deficiency. The frequency of PS deficiency in this study was 2.04% (Type I: 0.51%, Type II: 1.02%, Type III: 0.51%). Based on our findings, it would appear that the frequency of Type II PS deficiency in the Japanese population is approximately 1%. The screening of PS decrease should be judged by activity.

Identification of mutations in 15 Hungarian families with hereditary protein C deficiency

Hereditary protein C deficiency represents about 2-9% of inherited thrombophilias. Our aim was to elucidate the molecular basis of protein C deficiency in 25 members of 15 Hungarian families with venous thromboembolic diseases and to identify hitherto undescribed genetical defects in the protein C (PROC) gene. The exons of the PROC gene were screened for mutations with the combination of polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE), and/or PCR and single-strand conformation polymorphism (SSCP) analysis. The amplified DNA fragments with aberrant migration during DGGE and SSCP were sequenced. Mutations were determined in the PROC gene in all of the examined families: one nonsense mutation, one rare frameshift deletion and nine different missense mutations, of which three were novel (1493 A-->G, 35Asp-->Gly; 6231 G-->A, 173Gly-->Glu; 8476 C-->T, 254Thr-->Ile). The combination of hereditary protein C deficiency with other hereditary thrombophilias was rather common. DGGE and SSCP were proved to be efficient and cost-effective screening methods in the genetic analysis of hereditary protein C deficiency.

Limited Usefulness of Tests of Coagulation Defects for Predicting Symptomatic Pulmonary Embolism after an Initial Episode of Deep Vein Thrombosis

Objective:

To establish the usefulness of currently available tests of coagulation defects for predicting symptomatic pulmonary embolism (PE) in patients with lower extremity deep vein thrombosis (DVT).

Methods:

Between 1980 and 1996, 294 patients with DVT were followed for a mean period of 7.9 years. The coagulation defects included low activity of antithrom-bin III, protein C, protein S or plasminogen, and positivity for lupus anticoagulant or anticardiolipin antibody. The influences of these coagulation abnorm-alities on PE incidence were analysed, using a Cox regression hazards model.

Results:

Coagulation defects were found to be an important variable predicting PE (risk ratio = 7.272). ‘PE-free survival’ in patients with no coagulation defect was significantly longer than that in patients with one or more of these defects ( p = 0.0001). The sensitivity of coagulation tests for predicting PE was only 47% despite the negative predictive value of 93%.

Conclusions:

Determining these defects has limited usefulness in identifying patients who would be appropriate candidates for intensive anticoagulation therapy.

Venous thrombosis: a multicausal disease

The risk factors for venous thrombosis differ from those for arterial vascular disease. During the past 5 years, knowledge about the aetiology of venous thrombosis has advanced with the discovery of several factors that contribute to the incidence of thrombosis, particularly the role of coagulation abnormalities. These abnormalities are common in the general population and therefore will be present simultaneously in some individuals. The resultant gene-gene and gene-environment interactions between risk factors are the key to the understanding of why a certain person develops thrombosis at a specific point in time.

Risk of venous thromboembolism and clinical manifestations in carriers of antithrombin, protein C, protein S deficiency, or activated protein C resistance: a multicenter collaborative family study

Deficiencies of antithrombin (AT), protein C (PC) or protein S (PS), and activated protein C resistance (APCR) are very well-established coagulation defects predisposing to venous thromboembolism (VTE). We performed a retrospective cohort family study to assess the risk for VTE in individuals with AT, PC, or PS deficiency, or APCR. Five hundred thirteen relatives from 9 Italian centers were selected from 233 families in which the proband had had at least 1 episode of VTE. We calculated the incidence of VTE in the whole cohort and in the subgroups after stratification by age, sex, and defect. The overall incidence of VTE (per 100 patient-years) in the group of relatives was 0.52. It was 1.07 for AT, 0.54 for PC, 0.50 for PS, 0.30 for APCR, and 0.67 in the group with a double defect. The incidence was associated with age, but not with sex. The mean age at onset was between 30 and 40 years for all the coagulation defects. Women had the peak of incidence in the age range of 21 to 40 years, earlier than men. The lifetime risk for VTE was 4.4 for AT versus APCR, 2.6 for AT versus PS, 2.2 for AT versus PC, 1.9 for PC versus APCR, and 1.6 for PS versus APCR. AT deficiency seems to have a higher risk for VTE than the other genetic defects. There is a relation between age and occurrence of thrombosis for both men and women. The latter had the peak of incidence earlier than the former.

Acute Budd-Chiari Syndrome Associated with Activated Protein C Resistance During Intravenous Anticoagulant Treatment

The Budd-Chiari syndrome is a rare but serious condition defined as hepatic venous outflow obstruction. This article presents a case of acute Budd-Chiari syndrome in a 43-year-old woman with activated protein C resistance while she was being treated with intravenous heparin infusion for previously documented deep venous thrombosis. Activated protein C resistance caused by factor V Leiden mutation has emerged as the most prevalent hereditary cause of venous thromboembolism and should be considered as an etiologic factor in patients with Budd-Chiari syndrome.

Activated protein C resistance and deficiencies of antithrombin III, protein C or protein S and the risk of thromboembolic disease in users of oral contraceptives

The objective of this paper was to assess the risk of thrombosis in users of oral contraceptives. Furthermore, the sensitivity, specificity and predictive values of potential screening tests for the prediction of thromboembolic complications in users of oral contraceptives were calculated for the approximately six million German pill users. Despite high specificity, the predictive values of a positive family history, or evidence of either antithrombin III, protein C or protein S deficiency or resistance to activated protein C, are low due to the very low absolute risk of thrombosis among pill users. More than half of the 840 annual cases would pass the screening protocol undetected. A two-step screening protocol is suggested using family history as a selection criterion (thus reducing the need for laboratory screening by 85%) for laboratory investigation of activated protein C sensitivity and deficiencies of antithrombin III, protein C or protein S. Genotyping for factor V Leiden mutation is useful in cases with equivocal activated protein C sensitivities or to confirm a homozygous genotype.

Diagnosis of deep venous thrombosis and pulmonary embolism

Diagnostic evaluation in the patient with suspected deep vein thrombosis (DVT) and pulmonary embolism (PE) includes a clear correlation between clinical probability, test selection and test interpretation. Real-time B-mode ultrasound with color Doppler remains the imaging technique of choice in suspected DVT. The ventilation/perfusion (V/Q) lung scan is the preferred diagnostic modality in suspected PE. The D-dimer assay may be useful in excluding PA. New diagnostic techniques, including spiral computerized tomography may further modify the diagnostic algorithm.

Syndromes of thrombosis and hypercoagulability. Congenital and acquired causes of thrombosis

Blood coagulation protein and platelet defects are now known to account for up to ninety percent of unexplained venous thrombosis and up to seventy percent of unexplained arterial thrombotic or ischemic events. This article summarizes the common and uncommon blood protein and platelet defects which should be suspected, and searched for, in patients with such events. Defining such defects will have major impact on secondary prevention and duration of antithrombotic therapy in the afflicted patient and impact on primary prevention for identified family members in those harboring hereditary defects.

Association of vitamin K-dependent coagulation proteins and C4b binding protein with triglyceride-rich lipoproteins of human plasma

The triglyceride (TG) concentration in plasma is an independent risk factor for coronary heart disease. There is evidence that TG-rich lipoprotein (TGRLP), ie, chylomicrons (CMs), chylomicron remnants (CMRs), and VLDLs associate with factor VII and prothrombin and that the association enhances a platelet factor Xa-mediated prothrombin activation when the CM-prothrombin complex is exposed to platelets. In this study, we examined the association of the vitamin K-dependent coagulation factors VII, IX, X, and prothrombin, as well as the anticoagulation protein C and its cofactor protein S, in plasma lipoproteins obtained from human fasting and postprandial plasma. We also analyzed some other proteins that are related to the coagulation system but not to vitamin K-dependent proteins, including factor V, serum amyloid P component (SAP), C4b binding protein (C4BP), and thrombomodulin (TM), and as a control, Ig G. Human TGRLP (d < 1.006 kg/L), LDL (d = 1.006 to 1.063 kg/L), and HDL (d = 1.063 to 1.210 kg/L) were separated from normal subjects both in fasting and 2 to 3 hours after the ingestion of a meal containing 100 g fat. The different coagulation proteins, SAP, C4BP, TM, and Ig G were determined by SDS-polyacrylamide gel electrophoresis combined with Western blotting, using specific polyclonal or monoclonal antibodies, and were visualized by peroxidase staining. All the vitamin K-dependent proteins associate with TGRLP in both fasting and postprandial plasma, but not with LDL or HDL. Factor V, SAP, TM, and Ig G were not found in any lipoprotein classes. C4BP, which is a regulatory protein of the classic pathway of the complement system and which binds protein S in vivo to regulate blood coagulation, was present in TGRLP, especially postprandial, but not in LDL or HDL. The amounts of prothrombin, protein S, and C4BP in postprandial TGRLP were larger than those in fasting TGRLP. Vitamin K-dependent procoagulation and anticoagulation proteins, as well as C4BP, could be associated with TGRLP in vivo. If the association enhances prothrombin activation, this effect may thus be counteracted by simultaneous binding of protein S.

Inherited hypercoagulable states

Hypercoagulable states are a group of conditions associated with increased predisposition to thromboembolic events. Most of the inherited abnormalities recognized to date are associated with venous thromboembolism (VTE) rather than arterial thrombosis. The well-recognized inherited hypercoagulable states are the deficiencies of antithrombin, protein C and protein S, and the resistance to APC (factor V Leiden). These entities represent aberrations in the natural anticoagulant systems that exist in plasma. Other causes of inherited thrombophilia include abnormalities in the proteins of the fibrinolytic system, dysfibrinogenemias, deficiency of heparin cofactor II, abnormal thrombomodulin, elevated levels of histidine-rich glycoprotein, and the recently described variation in the prothrombin gene. One entity that has become firmly established as a predisposing factor for recurrent VTE is hyperhomocysteinemia. About half of VTE episodes in patients with inherited thrombophilias occur in relation to events that are generally recognized as predisposing states, such as surgery, pregnancy (particularly puerperium) and immobilization. In this review, the risks of VTE associated with inherited risk factors are discussed, and guidelines for the diagnosis and management are presented.

Activated protein C resistance in patients with central retinal vein occlusion

AIM/BACKGROUND

A new defect in the anticoagulant system has recently been discovered--activated protein C resistance. The frequency of this disorder has been shown to be increased in young patients (< 50 years of age) with central retinal vein occlusion. This study was carried out to determine if there was any overrepresentation of activated protein C resistance in patients > 50 years of age with central retinal vein occlusion.

METHODS

Blood samples were obtained from 83 patients > 50 years of age and with a history of central retinal vein occlusion. The blood samples were analysed for activated protein C resistance with standard clinical laboratory methods.

RESULTS

In this material 11% of the patients were resistant to activated protein C. The normal incidence of activated protein C resistance in the same geographical area is 10-11%.

CONCLUSION

Activated protein C resistance does not seem to be a cause of central retinal vein occlusion in people older than 50 years.

High prevalence of antithrombin III, protein C and protein S deficiency, but no factor V Leiden mutation in venous thrombophilic Chinese patients in Taiwan

We studied the prevalence of antithrombin III (AT III), protein C (PC) and protein S (PS) deficiencies and factor V Leiden mutation in thrombophilia in Taiwan. Eighty-five consecutive and unrelated patients with otherwise unexplained venous thrombophilia were studied. Both antigen and activity of inhibitors were determined using commercial kits (Stago), activated PC sensitivity ratio (APC SR) by Coatest (Chromogenix), and factor V mutation by polymerase chain reaction with sequence specific primer. Of 85 patients, 41 were male, 44 female, and mean age 49.4 years (17-82 years). None had factor V mutation, or APC SR of less than 2; 50 (58.8%) showed a deficiency of inhibitor proteins; 34 (68.0%) were hereditary, 16 (32.0%) non-hereditary; 3 had an AT III deficiency, 16 a PC deficiency, 28 a PS deficiency, and 3 a combined deficiency. Thirty-five were non-deficient without a known cause. The average age at the first thrombotic episode was 48.5 years (13-81 years). Thrombosis occurred spontaneously in 39 (78.0%) of 50 deficient patients. In conclusion, a relatively higher prevalence of AT III, PC and PS deficiency (59%), but no factor V Leiden mutation, was found in venous thrombophilic Chinese patients in Taiwan compared to that in western countries. Screening for inhibitor protein deficiency in Chinese thrombophilic patients is highly recommended.

Changes in activated protein C resistance during normal pregnancy

OBJECTIVE

The objective of this study was to determine the changes in activated protein C resistance that occur during normal pregnancy.

STUDY DESIGN

In this cross-sectional study activated protein C was measured in 128 women with normal pregnancies in the first, second, and third trimesters and in nonpregnant control subjects with 24 to 39 women in each group. In addition, factor V, factor VIII, free protein S, and functional protein C were measured and correlated with activated protein C levels. Polymerase chain reaction for factor V Leiden mutation was performed.

RESULTS

There was a significant fall in the activity of activated protein C in the second and third trimesters of pregnancy (p < 0.05). This was related to increased factor VIII and decreased free protein S levels (p = 0.002, R2 = 0.20). The prevalence of the factor V Leiden mutation was 7.3%.

CONCLUSION

Resistance to activated protein C is increased in the second and third trimesters of pregnancy. This is related to the alterations in other coagulation proteins, a phenomenon normally occurring during pregnancy.

Genetic and Phenotypic Analysis of a Large (122-Member) Protein S–Deficient Kindred Provides an Explanation for the Familial Coexistence of Type I and Type III Plasma Phenotypes

Protein S deficiency is a known risk factor for thrombosis. The coexistence of phenotypic type I (reduction in total and free antigen) and type III (reduction in free antigen only) protein S deficiencies in 14 of 18 families was recently reported. We investigated the cause of this phenotypic variation in the largest of these families (122 family members, including 44 affected individuals) using both molecular genetic and phenotypic analysis. We have identified a sole causative mutation (Gly295Val) in three family members representative of the variable phenotype. Complete cosegregation of the mutation with reduced free protein S antigen levels was found, regardless of the total antigen level. Analysis of phenotypic data showed high correlations between total protein S antigen and age in both normal and protein S–deficient family members, irrespective of gender. Free protein S antigen levels were not influenced by age, a finding explained by an association between β-chain containing C4b-binding protein (C4bBP-β+) antigen levels and age. We propose that the identified Gly295Val mutation causes quantitative, or type I, protein S deficiency, and that as age increases the total protein S antigen level normalizes with respect to the reference plasma pool, giving rise to a type III protein S–deficient phenotype.

The hypercoagulable state. Who, how, and when to test and treat

Patients with a family history of thrombosis, early-onset or recurring thrombosis, thrombosis at unusual sites, or warfarin-induced skin necrosis should be investigated for a possible underlying inherited hypercoagulable disorder. These include AT-III deficiency, protein C and S deficiencies, and APC resistance. Many patients should also be evaluated for the antiphospholipid syndrome, an acquired disorder. Functional assays are more useful than immunologic assays for diagnosing AT-III deficiency, protein C and S deficiencies, and APC resistance. A molecular probe is now available for the abnormal factor V most often responsible for APC resistance. Testing for the antiphospholipid syndrome involves assays for the lupus anticoagulant and anticardiolipin antibodies. AT-III and protein C concentrates are now available for short-term therapy. Long-term prophylactic administration of warfarin may have to be considered for some symptomatic patients with proven abnormalities, especially after more than one thrombotic event. While the management of asymptomatic persons remains controversial, the use of prophylactic anticoagulation should be anticipated for trauma, surgery, pregnancy, or other high-risk situations.

Absence of Linkage Between Type III Protein S Deficiency and the PROS1 and C4BP Genes in Families Carrying the Protein S Heerlen Allele

To elucidate the molecular basis of hereditary protein S (PS) deficiency and, in particular, type III or free PS deficiency, the allelic distribution and segregation patterns of the PS gene (PROS1) polymorphisms P626A/G and S460P (PS Heerlen) have been analyzed in a group of 45 proposita suffering from type I or type III PS deficiency. No differences between patients and controls were found in the frequency of the P626A/G alleles. By contrast, the frequency of the PS Heerlen allele in the group of patients with type III PS deficiency (9 of 46 chromosomes, P = .196) was significantly higher (P < .001) than in the control group (1 of 300 chromosomes, P = .003). The A allele of P626A/G was always associated with the P allele of S460P. However, this haplotype did not cosegregate with the type III PS-deficient phenotype in 3 of the families. Furthermore, multipoint linkage analysis excluded the whole PROS1 gene in 1 of these families, which is in agreement with the absence of mutations in the PROS1 gene, as determined by sequence analysis. Finally, linkage analysis with 4 microsatellite markers linked to the C4BPB and C4BPA loci also excluded these two genes. From these results we conclude that, at least in some families, the molecular basis of type III PS deficiency is not due to the Mendelian inheritance of a single defect in the PROS1 or in the C4BP genes.

Activated protein C resistance caused by factor V gene mutation: common coagulation defect in chronic venous leg ulcers?

Activated protein C resistance (APCR) may occur in up to one fourth of patients with venous leg ulcers and has recently emerged as the most frequent cause of venous thrombosis. Deep venous thrombosis often precedes deep venous insufficiency and is of major importance in the pathogenesis of venous leg ulcers. APCR is most frequently caused by a point mutation in the factor V gene (fV R506Q), resulting in reduced inactivation of activated factor V and imbalance of the hemostatic system. Recent data suggest that APCR/fV R506Q may be common in patients with venous leg ulcers. We review APCR as a genetically determined risk factor that may contribute to the development of venous leg ulcers. New diagnostic developments are discussed, and therapeutic guidelines specifically directed toward the prevention of thrombosis are suggested.

Identification of two novel point mutations in the human protein S gene associated with familial protein S deficiency and thrombosis

Individuals with thrombosis who were believed to possess associated familial protein S deficiency were analyzed for mutations in the protein S gene by a two-step process. First, the individuals were analyzed for protein S Pro626 A/G dimorphism in both their genomic DNA and reverse-transcribed (RT) polymerase chain reaction (PCR)-amplified cDNA from peripheral blood cell mRNA. If a heterozygote expressed both alleles at the mRNA level at this site in genomic DNA, a search for point mutations was made by direct cDNA sequencing. RT-PCR amplification of exons 1-6 with mRNA from two twin sisters, each of whom has severe type I protein S deficiency, revealed both larger and smaller fragments in addition to the expected 504-base pair fragment in normal individuals. A donor splicesite mutation at position +4 of the 5' end of intron A was subsequently identified in both sisters and their mother. This mutation would lead to incorrect precursor mRNA splicing and the observed cDNA products. Translation of the altered mRNAs would result in a truncated protein without biological activity. In a second family, cDNA sequencing revealed a T-->G mutation at codon 603 (Ile-->Ser) in exon 15 of the protein S gene in an individual with protein S deficiency (mixed type) and a history of thrombosis. The same mutation was also detected in the proband's mother and grandmother, both of whom also exhibit protein S deficiency and thrombotic disease. This mutation occurs within a disulfide loop of protein S that is believed to be responsible for binding to C4b binding protein and may result in greater affinity between protein S and C4b, consequently leading to thrombotic disease.