Laboratory testing for activated protein C resistance: rivaroxaban induced interference and a comparative evaluation of andexanet alfa and DOAC Stop to neutralise interference.

Background Investigation of hemostasis is problematic when patients are on anticoagulant therapy. Rivaroxaban especially causes substantial interference, extending many clot-based tests, thereby leading to false positive or negative events. In particular, rivaroxaban affects some assays for activated protein C resistance (APCR).

Reducing the effect of DOAC interference in laboratory testing for factor VIII and factor IX: A comparative study using DOAC Stop and andexanet alfa to neutralize rivaroxaban effects.

Introduction: Investigation of factors (F) VIII and IX is common, with testing important for diagnosis or exclusion of haemophilia A or B, associated acquired conditions and factor inhibitors. Rivaroxaban, a common direct anti-Xa agent, causes significant interference in clotting assays, including substantial false reduction of factor levels.

Aim: To assess whether rivaroxaban-induced interference of FVIII and FIX testing could be neutralized.

An update on quality control for the PFA-100/PFA-200.

Testing of platelet function comprises a crucial element of hemostasis assessment, particularly for investigations into bleeding and/or bruising. The Platelet Function Analyzer (PFA)-100 is the most utilized primary hemostasis-screening test system available, as recently remodeled/upgraded to the PFA-200. Internal quality control (IQC) and external quality assessment (EQA) (including proficiency testing) represent critical elements of ensuring test practice quality.

Differential sensitivity of von Willebrand factor activity assays to reduced VWF molecular weight forms: A large international cross-laboratory study.

Introduction: von Willebrand disease (VWD), the most common inherited bleeding disorder, is due to deficiencies/defects in von Willebrand factor (VWF). Effective diagnosis requires testing for FVIII, VWF antigen and one or more VWF 'activity' assays. Classically, 'activity' is assessed using ristocetin cofactor (VWF:RCo), but collagen binding (VWF:CB) and/or other assays are used by many laboratories.

Towards harmonization of external quality assessment/proficiency testing in hemostasis.

Quality in diagnostic testing represents a key target of laboratory medicine, for which an assurance around the quality of testing is expected from all involved in the process. Laboratories attempt to assure the quality of their testing by various processes, but especially by performance of internal quality control and external quality assessment (EQA). This is especially true for tests of hemostasis and coagulation.

Lack of grading agreement among international hemostasis external quality assessment programs.

: Laboratory quality programs rely on internal quality control and external quality assessment (EQA). EQA programs provide unknown specimens for the laboratory to test. The laboratory's result is compared with other (peer) laboratories performing the same test.

Overview of Hemostasis and Thrombosis and Contribution of Laboratory Testing to Diagnosis and Management of Hemostasis and Thrombosis Disorders.

Hemostasis is a complex and tightly regulated process whereby the body attempts to maintain a homeostatic balance to permit normal blood flow, without bleeding or thrombosis. When this balance is disrupted, due to trauma or underlying congenital bleeding or thrombotic disorders, clinical intervention may be required. To assist clinicians in diagnosing and managing affected patients, hemostasis laboratories offer an arsenal of tests, both routine (screening) and more specialized (diagnostic).

Explaining and reducing the variation in inter-laboratory reported values for International Normalised Ratio.

Introduction: Monitoring of vitamin K antagonist (VKA) therapy is usually achieved using the International Normalised Ratio (INR). However, despite international standardisation, there remains considerable concern regarding ongoing high levels of inter-laboratory variation, as generated by different laboratories using the same homogeneous plasma sample. Notably, significant discrepancies continue to be evidenced in external quality assessment (EQA) environments, prompting additional investigations to determine causes and to identify potential inconsistencies of practice.

The effect of the direct factor Xa inhibitors apixaban and rivaroxaban on haemostasis tests: a comprehensive assessment using in vitro and ex vivo samples.

The direct oral anticoagulants (DOACs), now including dabigatran, apixaban and rivaroxaban, have given clinicians alternative options to low molecular weight heparins (LMWHs) and vitamin K antagonist therapy, including warfarin, for the treatment of atrial fibrillation and treatment and prevention of venous thromboembolic (VTE) disease. DOACs have been successfully marketed as not requiring monitoring; however, there will be situations where clinicians will request laboratory testing, including emergency department admissions for haemorrhage or thrombosis, or emergency surgical interventions. We report the results of several Royal College of Pathologists of Australasia Quality Assurance Programs (RCPAQAP) surveys using apixaban and rivaroxaban spiked samples to either assess the suitability of certain potential screening or drug-quantifying assays, for assessment of drug presence or absence or measurement of levels, as well as assessing potential interference in a wide variety of haemostasis assays.

The effect of dabigatran on haemostasis tests: a comprehensive assessment using in vitro and ex vivo samples.

The new direct oral anticoagulants (DOACS) dabigatran, rivaroxaban, apixaban and edoxaban provide alternatives to warfarin for treatment and prevention of atrial fibrillation and venous thromboembolic disease in various settings. These have been developed as not requiring laboratory monitoring; however, under certain clinical situations, including recent haemorrhage/thrombosis, emergency surgical procedures, testing may be indicated.The aim of this study was to assess findings of haemostasis laboratory tests for one of the DOACs, dabigatran (Pradaxa), tested across a wide range of laboratory assays.

International normalized ratio monitoring of vitamin K antagonist therapy: comparative performance of point-of-care and laboratory-derived testing.

The monitoring of warfarin therapy using the international normalized ratio (INR) has now moved outside the laboratory's control by use of point-of-care (POC) devices. Although this provides patients with the convenience of immediate results and clinical assessment, POC-INRs are often performed by nonlaboratory staff with little experience in quality control. The Royal College of Pathologists of Australasia Quality Assurance Program (RCPAQAP) Haematology has devised a POC-INR external quality assessment (EQA) program that is suitable for both laboratory and nonlaboratory operators (e.

Evaluating errors in the laboratory identification of von Willebrand disease in the real world.

Introduction: von Willebrand disease (VWD), reportedly the most common bleeding disorder, arises from deficiency and/or defects of von Willebrand factor (VWF). Assessment requires a wide range of tests, including VWF activity and antigen. Appropriate diagnosis including differential identification of qualitative vs quantitative defects has important management implications, but remains problematic for many laboratories and clinicians.

External quality assessment/proficiency testing and internal quality control for the PFA-100 and PFA-200: an update.

Platelet function testing is an essential component of comprehensive hemostasis evaluation within the framework of bleeding and/or bruising investigations, and it may also be performed to evaluate antiplatelet medication effects. Globally, the platelet function analyzer (PFA)-100 (Siemens Healthcare, Marburg, Germany) is the most used primary hemostasis-screening instrument and has also been recently remodeled/upgraded to the PFA-200. The PFA-100 is sensitive to a wide range of associated disorders, including platelet function defects and von Willebrand disease (VWD), as well as to various antiplatelet medications.

Problems and solutions in laboratory testing for hemophilia.

A diagnosis of hemophilia A or hemophilia B begins with clinical assessment of the patient and is facilitated by laboratory testing. The influence of the latter on a diagnosis of hemophilia A or hemophilia B is clear-a diagnosis cannot be made without laboratory confirmation of a deficiency of factor FVIII (FVIII) or factor IX (FIX), respectively. Moreover, the degree of hemophilia severity is specifically characterized by laboratory test results.

External quality assessment of factor VIII inhibitor assays.

Inhibitors to coagulation factors cause prolongation of routine hemostasis laboratory test results and have clinical relevance in the management of congenital and acquired hemophilia patients. Factor VIII (FVIII) inhibitors can be either allo-antibodies (in hemophilia A) or auto-antibodies (in acquired hemophilia) directed against FVIII. The most commonly used assays for detecting these inhibitors are the classical Bethesda assay or a modified (Nijmegen) method.

External quality assurance for heparin monitoring.

Although there is considerable debate regarding the usefulness of laboratory heparin monitoring, these test processes reflect a substantial portion of hemostasis laboratory activity. Accordingly, external quality assurance (EQA) remains an essential component of such testing, and ensures that laboratories provide the best available service for patient management. This report provides an overview of recent and past EQA related to heparin monitoring using data from the Royal College of Pathologists of Australasia Haematology Quality Assurance Program, and heparin-containing plasma samples with concentrations ranging from 0 to 1.

Proficiency testing/external quality assurance for the PFA-100(®).

Background: Platelet function testing is integral to haemostasis investigations and the Platelet Function Analyser-100 (PFA-100(®)) is globally the most utilised primary haemostasis-screening instrument. External Quality Assurance (EQA) (or proficiency testing) is critical to ensuring quality of test practice, but EQA for platelet function is logistically challenging and actual test-challenges generally not possible.

Methods: A novel approach was therefore developed whereby a range of formulated test tubes are distributed to EQA participants to which citrated normal whole blood collected on site is added, thereby creating test material that can be locally evaluated.

Internal quality control and external quality assurance in testing for antiphospholipid antibodies: Part II--Lupus anticoagulant.

In addition to the presence of appropriate clinical features, the diagnosis of the antiphospholipid antibody syndrome (APS) fundamentally requires the finding of positive antiphospholipid antibody (aPL) test result(s), with these comprising clot-based assays for the identification of lupus anticoagulant (LA) and immunologic ("solid-phase") assays such as anticardiolipin antibodies (aCL) and anti-β2-glycoprotein I antibodies (aβ2GPI). This article is the second of two that review the process for, and provide recommendations to improve, internal quality control (IQC) and external quality assurance (EQA; or proficiency testing) for aPL assays. These processes are critical for ensuring the quality of laboratory test results, and thence the appropriate clinical diagnosis and management of APS.

Evaluating laboratory approaches to the identification of lupus anticoagulants: a diagnostic challenge from the RCPA Haematology QAP.

Background: Laboratory identification of lupus anticoagulants (LA), an important component of the clinical diagnosis of the autoimmune disorder antiphospholipid syndrome (APS), is challenged by the heterogeneity of tests available, the diagnostic and laboratory approach undertaken, and the heterogeneity of the autoantibodies present.

Aim: : To assess the laboratory approach for investigation of LA, as well as the utility of various tests and test approaches, given a difficult clinical scenario in which LA might or might not be present.

Methods: Ninety-three participants in the Royal College of Pathologists of Australasia (RCPA) Haematology Quality Assurance Program (QAP) were sent 4  mL of a complex but strongly positive LA sample blinded to the nature of the abnormality.

Diagnosis and management of von Willebrand disease in Australia.

Von Willebrand disease (VWD) is the most common inherited bleeding disorder and arises from deficiencies and/or defects in the plasma protein Von Willebrand factor (VWF). VWD is classified into six different types, with type 1 identifying a (partial) quantitative deficiency of VWF, type 3 defining a (virtual) total deficiency of VWF, and type 2 identifying four separate types (2A, 2B, 2M, and 2N) characterized by qualitative defects. The classification is based on phenotypic assays including factor VIII coagulant, VWF antigen, and VWF activity, primarily by ristocetin cofactor and collagen binding, as supplemented by additional testing.

Investigations from external quality assurance programs reveal a high degree of variation in the laboratory identification of coagulation factor inhibitors.

The laboratory has a key role in the initial detection of factor inhibitors and an ongoing role in the measurement of inhibitor titers during the course of inhibitor eradication therapy. The most commonly seen factor inhibitors are those directed against factor VIII (FVIII), usually detected either with the original or the Nijmegen-modified Bethesda assay. In addition, several circumstances can arise in which the laboratory may test samples that potentially reflect false identification of factor inhibitors.

Lower limit of assay sensitivity: an under-recognised and significant problem in von Willebrand disease identification and classification.

Unlabelled: von Willebrand disease (VWD) is the most common inherited bleeding ailment, and is characterised by low levels of, or abnormal function in, the plasma protein von Willebrand factor (VWF). However, the laboratory testing process is problematic because of both the heterogeneity of VWD and the limitations in the tests used to identify reduced or abnormal VWF.

Objective: This study reports on the lower levels of sensitivity for the different assays used in the diagnostic process for VWD and their significance in the diagnostic identification and classification ofVWD.

The diagnostic dilemma: dual presentations of clinical mucosal bleeding and venous thrombosis associated with the presence of thrombophilia markers and mild reduction in von Willebrand factor.

A prothrombotic and hemorrhagic state can separately manifest in one patient and can potentially cause several diagnostic problems. We report an intriguing case as an example of a potential hemostasis-based diagnostic dilemma. A 29-year-old female patient presented with a personal history of menorrhagia and other mucosal bleeding and renal ovarian thrombosis.