Laboratory Evaluation of Hypercoagulability

ROTEM could be useful for lupus anticoagulant hypoprothrombinemia syndrome

BACKGROUND

Lupus anticoagulant-hypoprothrombinemia syndrome (LAHPS) is a rare disease caused by acquired factor II (FII) deficiency and lupus anticoagulant. Patients with LAHPS typically present with thrombosis and bleeding. However, little information is available on the evaluation of coagulation potential in patients with LAHPS. We examined global coagulation potentials in patients with LAHPS during the clinical course in this study.

METHODS

Coagulation potentials in two pediatric patients with LAHPS were assessed by measuring clotting time (CT) and clot formation time using Ca2+-triggered rotational thromboelastometry (ROTEM), CT and maximum coagulation velocity using clot waveform analysis (CWA), and lag time and peak thrombin using the thrombin generation assay (TGA). The day of admission was defined as day 0.

RESULTS

In case 1, the bleeding symptoms disappeared by day 5. However, the TGA and CWA results were markedly lower than normal, although FII activity (FII:C) returned to within the normal range by day 14. In contrast, ROTEM revealed a recovery to near-normal levels (day 14). All coagulation parameters (day 80) were within normal ranges. In case 2, coagulation potential was severely depressed until day 12, although FII:C returned to normal levels. Bleeding symptoms disappeared on day 19, and the ROTEM data revealed that the parameters were close to the normal range. The coagulation parameters in all assays were normalized on day 75.

CONCLUSIONS

Recovery of coagulation potential in patients with LAHPS was slower than the recovery of FII:C. Moreover, ROTEM appeared to be clinically useful for assessing coagulation potential in patients with LAHPS.

Evaluation of Activated Protein C Resistance Using Thrombin Generation Test

Activated protein C (APC) resistance (APCR) has been identified as a risk factor of venous thromboembolism (VTE). A mutation at the level of factor (F) V has at first permitted the description of this phenotypic pattern and corresponded to a transition (guanine to adenine) at nucleotide 1691 in the gene coding for factor V, resulting in the replacement of arginine at position 506 by a glutamine. This confers to this mutated FV a resistance toward the proteolytic action of the complex formed by activated protein C with protein S. However, many other factors also lead to APCR, such as other F5 mutations (e.g., FV Hong Kong and FV Cambridge), protein S deficiency, elevated factor VIII, exogenous hormone use, pregnancy, and postpartum. All these conditions lead to the phenotypic expression of APCR and are associated with an increased risk of VTE. Considering the large population affected, the proper detection of this phenotype is a public health challenge. Currently, two types of tests are available: clotting time-based assays and their multiple variants and a thrombin generation-based assays and the endogenous thrombin potential (ETP)-based APCR assay. As APCR was thought to be uniquely related to the FV Leiden mutation, clotting time-based assays were specifically designed to detect this inherited condition. Nevertheless, other APCR conditions have been reported but were not captured by these clotting methods. Thus, the ETP-based APCR assay has been proposed as a global coagulation test able to these multiple APCR conditions, as it provides much more information, which makes it a potential candidate for screening coagulopathic conditions before therapeutic interventions. This chapter will describe the current method used for the realization of the ETP-based APC resistance assay.

Laboratory Testing for the Evaluation of Phenotypic Activated Protein C Resistance

Activated protein C (APC) resistance (APCR) is considered a risk factor of venous thromboembolism (VTE). The most common genetic disorder conferring APCR is a factor (F) V Leiden mutation, but many other factors are also implicated, such as other F5 mutations (e.g., FV Hong-Kong and FV Cambridge), protein S deficiency, elevated factor VIII, exogenous hormone use, pregnancy and postpartum, depending on how APCR is defined. Considering the large population affected, the detection of this phenotype is crucial. Two types of tests are currently available: clotting time-based assays (with several versions) and thrombin generation-based assays with the endogenous thrombin potential (ETP)-based assay. The purpose of this review is therefore to discuss the performances of these tests and the cases in which it would be appropriate to use one over the other. Initially, as APCR was thought to be solely related to the FV Leiden mutation, the objective was to obtain a 100% specific assay. Clotting-time based assays were thus specifically designed to detect this inherited condition. Later on, an APCR condition without a FV Leiden mutation was identified and highlighted as an independent risk factor of VTE. Therefore, the development of a less specific assay was needed and a global coagulation test was proposed, known as the ETP-based APCR assay. In light of the above, these tests should not be used for the same purpose. Clotting time-based assays should only be recommended as a screening test for the detection of FV mutations prior to confirmation by genetic testing. On the other hand, the ETP-based APC resistance assay, in addition to being able to detect any type of APCR, could be proposed as a global screening test as it assesses the entire coagulation process.

Laboratory Testing for the Evaluation of Phenotypic Activated Protein C Resistance

Activated protein C (APC) resistance (APCR) is considered a risk factor of venous thromboembolism (VTE). The most common genetic disorder conferring APCR is a factor (F) V Leiden mutation, but many other factors are also implicated, such as other F5 mutations (e.g., FV Hong-Kong and FV Cambridge), protein S deficiency, elevated factor VIII, exogenous hormone use, pregnancy and postpartum, depending on how APCR is defined. Considering the large population affected, the detection of this phenotype is crucial. Two types of tests are currently available: clotting time-based assays (with several versions) and thrombin generation-based assays with the endogenous thrombin potential (ETP)-based assay. The purpose of this review is therefore to discuss the performances of these tests and the cases in which it would be appropriate to use one over the other. Initially, as APCR was thought to be solely related to the FV Leiden mutation, the objective was to obtain a 100% specific assay. Clotting-time based assays were thus specifically designed to detect this inherited condition. Later on, an APCR condition without a FV Leiden mutation was identified and highlighted as an independent risk factor of VTE. Therefore, the development of a less specific assay was needed and a global coagulation test was proposed, known as the ETP-based APCR assay. In light of the above, these tests should not be used for the same purpose. Clotting time-based assays should only be recommended as a screening test for the detection of FV mutations prior to confirmation by genetic testing. On the other hand, the ETP-based APC resistance assay, in addition to being able to detect any type of APCR, could be proposed as a global screening test as it assesses the entire coagulation process.

Laboratory Testing for the Evaluation of Phenotypic Activated Protein C Resistance

Activated protein C (APC) resistance (APCR) is considered a risk factor of venous thromboembolism (VTE). The most common genetic disorder conferring APCR is a factor (F) V Leiden mutation, but many other factors are also implicated, such as other F5 mutations (e.g., FV Hong-Kong and FV Cambridge), protein S deficiency, elevated factor VIII, exogenous hormone use, pregnancy and postpartum, depending on how APCR is defined. Considering the large population affected, the detection of this phenotype is crucial. Two types of tests are currently available: clotting time-based assays (with several versions) and thrombin generation-based assays with the endogenous thrombin potential (ETP)-based assay. The purpose of this review is therefore to discuss the performances of these tests and the cases in which it would be appropriate to use one over the other. Initially, as APCR was thought to be solely related to the FV Leiden mutation, the objective was to obtain a 100% specific assay. Clotting-time based assays were thus specifically designed to detect this inherited condition. Later on, an APCR condition without a FV Leiden mutation was identified and highlighted as an independent risk factor of VTE. Therefore, the development of a less specific assay was needed and a global coagulation test was proposed, known as the ETP-based APCR assay. In light of the above, these tests should not be used for the same purpose. Clotting time-based assays should only be recommended as a screening test for the detection of FV mutations prior to confirmation by genetic testing. On the other hand, the ETP-based APC resistance assay, in addition to being able to detect any type of APCR, could be proposed as a global screening test as it assesses the entire coagulation process.

Apixaban Does Not Interfere With Protein S or Activated Protein C Resistance (Factor V Leiden) Testing Using aPTT-Based Methods

CONTEXT.—

Apixaban causes a false increase in activated protein C resistance (APCR) ratios and possibly protein S activity.

OBJECTIVE.—

To investigate whether this increase can mask a diagnosis of factor V Leiden (FVL) or protein S deficiency in an actual population of patients undergoing apixaban treatment and hypercoagulation testing.

DESIGN.—

During a 4.5-year period involving 58 patients, we compared the following 4 groups: heterozygous for FVL (FVL-HET)/taking apixaban, wild-type/taking apixaban, heterozygous for FVL/no apixaban, and normal APCR/no apixaban. Patients taking apixaban were also tested for protein S functional activity and free antigen (n = 40).

RESULTS.—

FVL-HET patients taking apixaban had lower APCR ratios than wild-type patients (P < .001). Activated protein C resistance in FVL-HET patients taking apixaban fell more than 3 SD below the cutoff of 2.2 at which the laboratory reflexes FVL DNA testing. No cases of FVL were missed despite apixaban. In contrast to rivaroxaban, apixaban did not interfere with the assessment of protein S activity (mean activity 93.9 IU/dL, free antigen 93.1 IU/dL, P = .39). A total of 3 of 40 patients (8%) had low free protein S antigen (30, 55, and 57 IU/dL), with correspondingly similar activity results (27, 59, and 52 IU/dL, respectively). Apixaban did not cause a missed diagnosis of protein S deficiency.

CONCLUSIONS.—

Despite apixaban treatment, APCR testing can distinguish FVL-HET from healthy patients, rendering indiscriminate FVL DNA testing of all patients on apixaban unnecessary. Apixaban did not affect protein S activity.

Pulmonary Infarction due to Paget-Schroetter Syndrome and Nephrotic Syndrome

Patient: Male, 23

Final Diagnosis: Minimal change disease

Symptoms: Right arm and neck swelling

Medication: —

Clinical Procedure: Catheter-directed thrombolysis

Specialty: Cardiology

Rivaroxaban Causes Missed Diagnosis of Protein S Deficiency but Not of Activated Protein C Resistance (Factor V Leiden)

Context.—

Rivaroxaban causes a false increase in activated protein C resistance (APCR) ratios and protein S activity.

Objective.—

To investigate whether this increase masks a diagnosis of factor V Leiden (FVL) or protein S deficiency in a “real-world” population of patients undergoing rivaroxaban treatment and hypercoagulation testing.

Design.—

During a 2.5-year period, we compared 4 groups of patients (n = 60): FVL heterozygous (FVL-HET)/taking rivaroxaban, wild-type/taking rivaroxaban, FVL-HET/no rivaroxaban, and normal APCR/no rivaroxaban. Patients taking rivaroxaban were tested for protein S functional activity and free antigen (n = 32).

Results.—

The FVL-HET patients taking rivaroxaban had lower APCR ratios than wild-type patients (P &lt; .001). For FVL-HET patients taking rivaroxaban, mean APCR was 1.75 ± 0.12, versus 1.64 ± 0.3 in FVL-HET patients not taking rivaroxaban (P = .005). Activated protein C resistance in FVL-HET patients fell more than 3 SDs below the cutoff of 2.2 at which the laboratory reflexes FVL DNA testing. No cases of FVL were missed despite rivaroxaban. In contrast, rivaroxaban falsely elevated functional protein S activity, regardless of the presence or absence of FVL (P &lt; .001). A total of 4 of 32 patients (12.5%) had low free protein S antigen (range, 58%–67%), whereas their functional protein S activity appeared normal (range 75%–130%). Rivaroxaban would have caused a missed diagnosis of all cases of protein S deficiency during the study if testing relied on the protein S activity assay alone.

Conclusions.—

Despite rivaroxaban treatment, APCR testing can distinguish FVL-HET from normal patients, rendering indiscriminate FVL DNA testing of all patients on rivaroxaban unnecessary. Free protein S should be tested in patients taking rivaroxaban to exclude hereditary protein S deficiency.

Diagnosis and management of factor V Leiden

INTRODUCTION

The discovery of the factor V Leiden (FVL) missense mutation (Arg506Gln) causing factor V resistance to the anticoagulant action of activated protein C was a landmark that allowed a better understanding of the basis of inherited thrombotic risk. FVL mutation is currently the most common known hereditary defect predisposing to venous thrombosis. Areas covered: Novel data-driven FVL diagnosis and therapeutic approaches in the management of FVL carriers in various clinical settings. Brief conclusions on topics of direct clinical relevance including currently available indications for primary and secondary prophylaxis, the management of female, pediatric carriers and asymptomatic relatives. Latest evidence on the association between FVL and cancer, as well as the possible use of direct oral anticoagulant therapy. Expert commentary: Although FVL diagnosis nowadays is highly accurate, many doubts remain regarding the best management and therapeutic protocols. The main role of clinicians is to tailor therapeutic strategies to carriers and their relatives. High familial penetrance, distinctive aspects of the first thrombotic event (provoked/unprovoked, age, etc.) and laboratory biomarkers can guide the optimal management of secondary antithrombotic prophylaxis, primary prophylaxis in asymptomatic individuals, and whether to screen relatives.

Factor V Leiden

Factor V Leiden (FVLeiden ) is a common hereditary thrombophilia that causes activated protein C (APC) resistance. This review describes many of the most fascinating features of FVLeiden , including background features, mechanisms of hypercoagulability, the founder mutation concept, the "FVLeiden paradox," synergistic interaction with other thrombotic risk factors, the intertwined relationship between FVLeiden and APC resistance testing, and other, uncommon mutations implicated in causing APC resistance. In addition, there are several conditions where laboratory tests for APC resistance and FVLeiden are or can be discrepant, including lupus anticoagulants, anticoagulants such as direct thrombin inhibitors (dabigatran, argatroban, and bivalirudin) and rivaroxaban, as well as pseudohomozygous, pseudo-wildtype, liver transplant, and bone marrow transplant patients. The laboratory test error rate for FVLeiden is also presented.

Activated protein C resistance testing for factor V Leiden

Activated protein C resistance assays can detect factor V Leiden with high accuracy, depending on the method used. Factor Xa inhibitors such as rivaroxaban and direct thrombin inhibitors including dabigatran, argatroban, and bivalirudin can cause falsely normal results. Lupus anticoagulants can cause incorrect results in most current assays. Assays that include dilution into factor V-deficient plasma are needed to avoid interference from factor deficiencies or elevations, which can arise from a wide variety of conditions such as warfarin, liver dysfunction, or pregnancy. The pros and cons of the currently available assays are discussed.

Hypercoagulable states: an algorithmic approach to laboratory testing and update on monitoring of direct oral anticoagulants

Hypercoagulability can result from a variety of inherited and, more commonly, acquired conditions. Testing for the underlying cause of thrombosis in a patient is complicated both by the number and variety of clinical conditions that can cause hypercoagulability as well as the many potential assay interferences. Using an algorithmic approach to hypercoagulability testing provides the ability to tailor assay selection to the clinical scenario. It also reduces the number of unnecessary tests performed, saving cost and time, and preventing potential false results. New oral anticoagulants are powerful tools for managing hypercoagulable patients; however, their use introduces new challenges in terms of test interpretation and therapeutic monitoring. The coagulation laboratory plays an essential role in testing for and treating hypercoagulable states. The input of laboratory professionals is necessary to guide appropriate testing and synthesize interpretation of results.

The Utility of Platelet and Coagulation Testing of Antithrombotics: Fusing Science with Patient Care

[Table: see text] There is an increasing need for the standardization of platelet function and coagulation testing for the assessment of antithrombotic therapies. Investigators continue to strive to identify ideal laboratory testing and monitoring procedures for acquired and inherited platelet function defects as well as for evaluating patient status when treated with existing or emerging antithrombotics. These therapies are used primarily in the treatment of ischemic complications. In patients receiving antithrombotic therapy, the balance between hemostasis and thrombosis is a challenge as there is an ongoing risk for bleeding when patients are receiving antiplatelet agents or anticoagulants to lessen their risk for secondary thrombotic events. There are several diverse tests for monitoring anticoagulant therapy; however, as new agents are developed, more specific tests will be required to directly assess these agents in relationship to overall coagulation status. Research in the platelet biology field is ongoing to provide point-of-care methodologies for the assessment of platelet reactivity in terms of both bleeding and thrombosis risk. Currently there are no instruments that reliably assess the risk of bleeding. The challenges that routinely faced are the complexity of physiology, the need for standardization of platelet testing methodology, and the necessity for appropriate interpretation of the test results.

The isolated prolonged PTT

It is increasingly difficult to choose the proper tests to investigate an abnormal laboratory result, delaying the time to reach the correct diagnosis and increasing the cost of care. A wrong choice may also lead to clinically significant errors, which can be life threatening. To show how errors in test selection occur in routine medical practice, the authors describe an algorithm to evaluate patients with a prolonged activated partial thromboplastin time (PTT) and a normal prothrombin time. This exercise challenges the commonly held belief that errors in laboratory utilization occur primarily with esoteric and/or genetic testing, rather than in patients with common abnormalities such as a prolonged PTT.

Low borderline plasma levels of antithrombin, protein C and protein S are risk factors for venous thromboembolism

BACKGROUND

Inherited deficiencies of antithrombin (AT), protein C (PC) and protein S (PS) are risk factors for venous thromboembolism (VTE). They are usually defined by laboratory cut-offs (in our setting 81, 70 and 63 IU dL(-1), respectively), which give only a rough idea of the VTE risk associated with plasma levels of these proteins.

OBJECTIVES

 We investigated whether the risk of VTE associated with the plasma deficiencies of AT, PC or PS has a dose-response effect, and whether low borderline levels of these proteins are associated with an increased risk of VTE, both in the whole study population and separately in carriers of either factor V Leiden or G20210A prothrombin gene mutation.

PATIENTS/METHODS

A case-control study of 1401 patients with a first objectively-documented VTE and 1847 healthy controls has been carried out.

RESULTS

A dose-response effect on the VTE risk was observed for all the three anticoagulant proteins. Compared with individuals with AT, PC or PS levels > 100 IU/dL, the adjusted odds ratio (95% CI) of VTE was 2.00 (1.44-2.78) for AT levels between 76 and 85 IUdL(-1) , 2.21 (1.54-3.18) and 1.84 (1.31-2.59) for PC and PS levels between 61 and 75 IUdL(-1) . The risk of unprovoked VTE in factor V Leiden or prothrombin G20210A carriers appears 2 to 3-fold increased when levels of AT or PS are low borderline.

CONCLUSIONS

 Low borderline plasma levels of AT, PC and PS are associated with a 2-fold increased risk of VTE and should be considered in the assessment of the individual VTE risk.

Protein C assay performance: an analysis of North American specialized coagulation laboratory association proficiency testing results

To determine the performance and frequency of protein C reagents currently used by clinical laboratories, we analyzed North American Specialized Coagulation Laboratory Association (NASCOLA) protein C proficiency testing data from 6 surveys conducted in 2009 and 2010 (2009-1 to 2009-3 and 2010-1 to 2010-3). Interlaboratory coefficients of variation (CV) for commonly used reagents on a survey with normal protein C ranged from 8% to 12% for antigenic assays, from 4% to 7% for chromogenic activity assays, and from 7% to 22% for clot-based activity assays. CVs for commonly used reagents on specimens with abnormal protein C ranged from 15% to 24% for antigenic, 4% to 11% for chromogenic, and 10% to 17% for clot-based assays (averaged across 3 surveys). Some reagents were used by relatively few laboratories and therefore additional study may be needed for those reagents. For all commonly used reagents, biases were usually small and often not statistically significant. All assessed reagents were clinically accurate, and were considered acceptable options for a specialized coagulation laboratory.

Advances in laboratory testing for thrombophilia

Testing for hereditary thrombophilia typically includes tests for activated protein C resistance (APC-R) and/or factor V Leiden, protein C, protein S, antithrombin, and prothrombin G20210A. New options for these assays have become available in recent years, with different advantages and disadvantages among the currently available methods. Potential interferences for each assay type are discussed, including lupus anticoagulants, heparin, warfarin, direct thrombin inhibitors (such as argatroban, dabigatran, hirudin, or bivalirudin), rivaroxaban, factor deficiencies or elevations, factor V Leiden, and specific mutations that the assay(s) might not be able to detect. Causes of acquired deficiencies are also described, as these must be carefully excluded before diagnosing a hereditary deficiency of protein C, protein S, or antithrombin.

Pathology consultation on the laboratory evaluation of thrombophilia: when, how, and why

Venous thromboembolism (VTE) results from the interaction of the Virchow triad (venous stasis, endothelial injury, and hypercoagulability). Risk factors for increased hypercoagulability, or thrombophilia, include activated protein C resistance/factor V Leiden, the prothrombin G20210A mutation, deficiencies of the natural anticoagulants (antithrombin, proteins C and S), antiphospholipid antibodies, hyperhomocysteinemia, and increased factor VIII activity. Not all patients with VTE need to be tested for such risk factors, but patients with thrombophilia should be evaluated for all possibilities to better estimate risk. At the same time, testing should be patient-specific because assay results are affected by preanalytic variables, including thrombosis and anticoagulant therapy.

Delay in diagnosis of cerebral venous and sinus thrombosis: successful use of mechanical thrombectomy and thrombolysis

Cerebral venous and sinus thrombosis is a relatively rare condition with a variable presentation that can translate into a difficult workup and a delay in diagnosis and treatment. We describe the successful use of mechanical thrombectomy and thrombolysis in the case of an eighteen-year-old woman that presented with progressive thrombosis of the jugular veins and dural sinuses despite adequate anticoagulation. Our case highlights the need for clinicians to include CVST in the initial differential diagnosis of patients in order to prevent delays and poor outcomes.

Protein S abnormalities: a diagnostic nightmare

Heterozygous deficiency of Protein S (PS) increases the risk for developing thrombosis. Many acquired conditions alter plasma PS levels. These complex interactions of PS in plasma make it imperative that clinical PS assay limitations are understood so that the assays are reliable, reproducible and specific to diagnose true genetic abnormalities based on plasma phenotype alone. Unfortunately, the diagnosis of PS deficiency is difficult and complicated. Three basic assays can be utilized for assessing PS in plasma: PS activity assay, Free PS antigen assay, and Total PS antigen assay. This article will review these clinical assays and their associated problems. We also discuss the confounding and interfering factors that make it difficult to obtain an accurate diagnosis of PS deficiency.

Diagnostic algorithm for thrombophilia screening

Thrombophilia screening is aimed at detecting the most frequent and well-defined causes of venous thrombosis, such as activated protein C resistance/factor V Leiden mutation, prothrombin G20210A gene mutation, deficiencies of natural anticoagulants, such as antithrombin, protein C and protein S, the presence of antiphospholipid antibodies, hyperhomocysteinemia and increased factor VIII activity. At this time, thrombophilia screening is not recommended for those possible congenital or acquired risk factors, whose association with increased risk of thrombosis has not been proven sufficiently. Laboratory investigations should include a step-wise approach to the diagnosis of thrombotic disorders with respect to the assays and methods of analysis that are used. The assays recommended for the first diagnostic step of screening should establish, whether the subject has one of the common causes of thrombophilia. If one or more abnormal results are obtained, the second diagnostic step includes the assays recommended for confirmation and/or characterization of the defect. When performing the investigation of thrombophilia, it is important to consider all pre-analytical and other variables that may affect the results of thrombophilia testing, including time of testing, age, gender, liver function, hormonal status, pregnancy or the acute phase response to inflammatory diseases. This is necessary, in order to avoid, any misinterpretation of the results. This review summarizes the current knowledge concerning thrombophilia investigations, with special focus on the diagnostic algorithm regarding patient selection, the assays and methods of analysis used and all the variables that should be considered when employing tests for the diagnosis of thrombophilia.

Death after liposuction: case report and review of the literature

We report the case of a 41-year-old woman who died after surgical intervention for liposuction. The case was studied by a methodological approach including examination of clinical records and documentation, analysis of anatomo-histopathological findings and evaluation of physicians' behaviour. Autopsy excluded the lethal complications most frequently associated with liposuction (pulmonary embolism, sepsis, necrotizing fasciitis, perforation of abdominal organs) and identified the cause of death as 'massive necrosis of brain-stem and cerebellum, due to spontaneous thrombosis of the basilar and cerebellar district'. Analysis of the physicians' behaviour, together with a review of the literature, excluded medical errors or malpractice. The Court of Law ruled the death as a fatal unforeseeable complication of the operation. The medico-legal interest of the case lies in the singular anatomo-pathological cause of death, discussed in relation to the hypothesis of professional responsibility after surgical intervention for liposuction.