Preanalytical issues that may cause misdiagnosis in haemophilia and von Willebrand disease

Laboratory diagnosis of von Willebrand disease in the age of the new guidelines: considerations based on geography and resources

von Willebrand disease (VWD) is considered the most common bleeding disorder and arises from deficiency and/or defect in the adhesive plasma protein von Willebrand factor (VWF). Diagnosis of VWD requires clinical assessment and is facilitated by laboratory testing. Several guidelines for VWD diagnosis exist, with the latest American Society of Hematology, International Society on Thrombosis and Haemostasis, National Hemophilia Foundation, and World Federation of Hemophilia 2021 guidelines presenting 11 recommendations, some of which have drawn controversy. In the current narrative review, we provide additional context around difficulties in laboratory diagnosis/exclusion/typing of VWD, with a focus on developing countries/resource-poor settings. In particular, there are many variations in assay methodology, and some methods express high assay variability and poor low-level VWF sensitivity that compromises their utility. Although we favor an initial 4-test assay panel, comprising factor (F) VIII coagulant activity, VWF antigen, VWF glycoprotein Ib binding (VWF:GPIbR or VWF:GPIbM favored over VWF Ristocetin cofactor) and VWF collagen binding, we also provide strategies for laboratories only able to incorporate an initial 3-test assay panel, as favored by the latest guidelines, to improve diagnostic accuracy.

Laboratory Testing for von Willebrand Disease Using a Composite Rapid 3-Test Chemiluminescence-Based von Willebrand Factor Assay Panel

von Willebrand disease (VWD) is the most commonly reported inherited bleeding disorder and may alternatively occur as an acquired von Willebrand syndrome (AVWS). VWD/AVWS develops from defects and/or deficiency in the adhesive plasma protein von Willebrand factor (VWF). VWD/AVWS diagnosis/exclusion remains challenging because of the heterogeneity of VWF defects and the technical limitations of many VWF tests, as well as the VWF test panels (number and type of tests) chosen by many laboratories. Laboratory testing for these disorders utilizes evaluation of VWF level and activity, with activity assessment needing several tests due to the many functions performed by VWF in order to help counteract bleeding. This report explains procedures for evaluating VWF level (antigen; VWF:Ag) and activity by means of a chemiluminescence-based panel. Activity assays comprise collagen binding (VWF:CB) and a ristocetin-based recombinant glycoprotein Ib-binding (VWF:GPIbR) assay that reflects a contemporary alternative to classical ristocetin cofactor (VWF:RCo). This 3-test VWF panel (Ag, CB, GPIbR [RCo]) reflects the only such composite panel available on a single platform and is performed on an AcuStar instrument (Werfen/Instrumentation Laboratory). Certain regional approvals may also allow this 3-test VWF panel to be performed on the BioFlash instrument (Werfen/Instrumentation Laboratory).

Features of clinical and laboratory diagnosis of rare coagulopathy – acquired hemophilia

Introduction. The formation of circulating autoantibodies capable of inhibiting factors of the blood coagulation system is accompanied by the occurrence of spontaneous and/or post-traumatic bleeding in patients without a history of previous disorders of the hemostasis system. One of the reasons for the development of such conditions is acquired hemophilia.

Aim – to present algorithms for laboratory diagnosis of acquired hemophilia.

Main findings. Primary diagnosis and control of therapy of the disease are carried out based on the results of coagulation studies, the decoding and interpretation of which often causes difficulties due to the low awareness of doctors about the algorithms for laboratory diagnosis and tactics for managing patients. In acquired hemophilia there is no direct relationship between the results of laboratory tests and the clinical manifestations of the disease, which is determined by the kinetics of the interaction of autoantibodies with blood coagulation factor (F) VIII. There is a «false» in vitro decrease in the activity of factors of the internal pathway (FIX, FXI and FXII), associated with the effect of a rapid inhibitor in high titers. An important laboratory task is the determination of lupus anticoagulant, which makes it difficult to timely diagnose and verify the diagnosis.

Should multiple factor dilutions be performed for all patient coagulation factor assays? Let the debate begin!

Laboratory assessment of blood coagulation factors may be undertaken for various reasons, including investigating the possibility of hemophilia or unexpected prolongation in routine coagulation assays (eg, prothrombin time, activated partial thromboplastin time). Several guidelines recommend performing multiple dilutions (usually 2-3) on all patient test samples to evaluate "parallelism" as a guide to the presence of potential "inhibitors," be they factor inhibitors, lupus anticoagulant, or related to the presence of anticoagulant therapy. The current Forum argues against mandating investigation of parallelism (or multiple dilutions) for all samples destined for testing, instead suggesting that a more targeted approach will likely provide better clinical utility and use of laboratory resources.

Why is Misdiagnosis of von Willebrand Disease Still Prevalent and How Can We Overcome It? A Focus on Clinical Considerations and Recommendations

Despite von Willebrand disease (VWD) being the most common inherited bleeding disorder, its accurate diagnosis is frequently shrouded by diagnostic pitfalls. VWD is frequently under-diagnosed, over-diagnosed and misdiagnosed, leading to significant avoidable patient morbidity and health care system burden. At the heart of this dilemma lies the heterogeneity and complexity of von Willebrand factor (VWF) and associated defects, and the necessity of coalescing clinical and laboratory features to obtain an accurate diagnosis. Common pitfalls include poor clinical and scientific understanding and familiarity with VWD, incomplete clinical history and lack of routine use of standardised bleeding assessment tools (BAT), difficulty in accessing a comprehensive repertoire of laboratory tests, significant pre-analytical, analytical and post-analytical issues, and lack of expertise in laboratory testing and interpretation. Errors, resulting in under-diagnosis, over-diagnosis, and misdiagnosis of VWD, are presented and discussed. Strategies to minimise errors include better education of clinicians and laboratory staff on VWD, routine use of validated BAT, utilising a comprehensive gamut of laboratory investigations according to a standardised algorithm, and repeating testing to minimise pre-analytical errors. Recommendations on appropriate patient selection for VWD testing, how VWD should be investigated in the laboratory, and how to ensure test results are accurately interpreted in the correct clinical context are detailed.

New Developments in Diagnosis and Management of Acquired Hemophilia and Acquired von Willebrand Syndrome

Acquired hemophilia A and acquired von Willebrand syndrome are rare, but life-threatening bleeding disorders that require prompt diagnosis and treatment by hematologists. Acquired hemophilia A is defined as an acquired severe bleeding tendency caused by autoantibody formation against coagulation factor VIII. Acquired von Willebrand syndrome is characterized by a new onset bleeding tendency caused by a reduced concentration and/or function of von Willebrand factor. These disorders are associated with a variety of underlying disorders, including various hematological malignancies, for example, plasma cell disorders, lymphoproliferative disorders, monoclonal gammopathy of undetermined significance, and myeloproliferative neoplasms. It is of utmost important to recognize these acquired bleeding disorders in these patients who are at risk for severe bleeding, and to perform additional diagnostic hemostasis laboratory evaluation. This will enable immediate diagnosis of the acquired bleeding disorder and management of both the bleeding episodes and the causative underlying disorder. In recent years, several new etiological factors for acquired hemophilia A, such as treatment with immune checkpoint inhibitors or DPP-4 inhibitors and SARS-CoV2 infection, and for acquired von Willebrand syndrome, for example, left ventricular assist devices, have been identified and also new treatment options have become available. In this concise review, the most recent data on etiology, diagnosis, and treatment of acquired bleeding disorders are presented and discussed.

Overutilization in laboratory medicine: tackling the problem with quality improvement science

Overutilization of tests and treatments is a widespread problem in contemporary heath care, and laboratory medicine is no exception. It is estimated that 10-70% of laboratory tests may be unnecessary, with estimates in the literature varying depending on the situation and the laboratory test. Inappropriate use of laboratory tests can lead to further unnecessary testing, adverse events, inaccurate diagnoses, and inappropriate treatments. Altogether, this increases the risk of harm to a patient, which can be physical, psychological, or financial in nature. Overutilization in healthcare is driven by complex factors including care delivery models, litigious practice environments, and medical and patient culture. Quality improvement (QI) methods can help to tackle overutilization. In this review, we outline the global healthcare problem of laboratory overutilization, particularly in the developed world, and describe how an understanding of and application of quality improvement principles can help to address this challenge.

How we diagnose 2M von Willebrand disease (VWD): Use of a strategic algorithmic approach to distinguish 2M VWD from other VWD types

INTRODUCTION

von Willebrand disease (VWD) is the most common inherited bleeding disorder and caused by an absence, deficiency or defect in von Willebrand factor (VWF). VWD is currently classified into six different types: 1, 2A, 2B, 2N, 2M, 3. Notably, 2M VWD is more often misdiagnosed as 2A or type 1 VWD than properly identified as 2M VWD.

AIM

To describe an algorithmic approach to better ensure appropriate identification of 2M VWD, and reduce its misdiagnosis, as supported by sequential laboratory testing.

METHODS

Comparative assessment of types 1, 2A, 2B and 2M VWD using various laboratory tests, including VWF antigen and several VWF activity assays, plus DDAVP challenge data, ristocetin-induced platelet agglutination (RIPA) data, multimer analysis and genetic testing.

RESULTS

Types 1, 2A, 2B and 2M VWD give characteristic test patterns that can provisionally classify patients into particular VWD types. Notably, type 1 VWD shows low levels of VWF, but VWF functional concordance (VWF activity/Ag ratios >0.6), with both baseline assessment and post-DDAVP. Types 2A, 2B and 2M VWD show VWF functional discordance (low VWF activity/Ag ratio(s)) dependent on the defect, but type 2M separates from 2A/2B VWD based on specific test patterns, especially with collagen binding vs glycoprotein Ib binding assays. RIPA identifies 2B VWD. Multimers separate 2M from 2A/2B.

CONCLUSION

We provide strategies to improve correct diagnosis of VWD, especially focussed on 2M VWD, and which can be used by most diagnostic haemostasis laboratories, reserving genetic analysis (if required) for confirmation.

The spatial distribution of the normal reference values of the activated partial thromboplastin time based on ArcGIS and GeoDA

We explored the variation and spatial distribution of the activated partial thromboplastin time (APTT) reference values of healthy people at different altitudes in China in order to develop a scientific basis for a unified standard. The APTT reference values of 49,020 healthy males (41-75 years old) and 32,447 healthy females (41-75 years old) were collected from 601 work units and 546 work units in China, respectively. The relationship between the APTT reference values and altitude was tested by correlation analysis. Linear regression analysis and curve analysis were employed to predict the APTT reference values in the whole country. Trend surface analysis, the variation function, kriging interpolation, and Getis-Ord Gi* statistic were utilized to reveal the spatial characteristics of the values. The result showed a significant positive correlation between the APTT reference values and altitude. The APTT values for females were prolonged for a greater amount of time than the males in several same areas in China. The spatial contact forms of the APTT reference values of healthy Chinese were mainly "high-high" and "low-low," which was in accord with the first law of geography. The APTT reference values still showed spatial autocorrelation and regional variation. The values were higher in the western and northern areas than in the eastern and southern areas of China. The APTT reference values of people aged 41-75 in China showed regional differences. The APTT reference values in one area can be estimated by using the best prediction model or can be obtained by the geographical distribution.

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.

MATERIALS AND METHODS

An international, cross-laboratory exercise for FVIII (n = 84) and FIX (n = 74), using four samples: (A) pool of normal plasma; (B) pool spiked with rivaroxaban (200 ng/mL); (C) rivaroxaban sample subsequently treated with 'DOAC Stop' and; (D) rivaroxaban sample treated with andexanet alfa (200 μg/mL). Testing performed blind to sample type.

RESULTS

All laboratories reported normal FIX and 94% reported normal FVIII in the pool sample. Instead, 55% and 95%, respectively, reported abnormal FIX and FVIII levels for the rivaroxaban sample. DOAC Stop treatment evidenced a correction in most laboratories (100% reported normal FIX and 86% normal FVIII). Andexanet alfa provided intermediate results, with many laboratories still reporting abnormal results (59% for FVIII, 18% for FIX). We also identified reagent-specific issues.

CONCLUSIONS

As expected, rivaroxaban caused false low values of FVIII and FIX. This might lead to increased testing to identify the cause of low factor levels and potentially lead to false identification of (mild) haemophilia A or B if unrecognized by clinicians/laboratories. DOAC Stop effectively neutralized the rivaroxaban effect, but andexanet alfa less so, with reagent-related effects evident, and thus, false low values sometimes persisted.

Two cases of von Willebrand disease type 3 in consanguineous Chinese families

BACKGROUND

von Willebrand disease (VWD) is the most common inherited bleeding disorder caused by defective or deficient von Willebrand factor (VWF). VWD type 3 is inherited in autosomal recessive manner. We described clinical and molecular features of VWD type 3 in two consanguineous marriage families.

METHODS

Peripheral blood was collected, PT, APTT, FVIII:C, VWF:RCo, VWF:Ag were measured. A targeted next-generation sequencing panel covering F8, F9, and VWF genes was applied followed by Sanger sequencing.

RESULTS

Both families had a baby die in their first year due to bleeding disorders. A 23-year-old female patient from family A suffered menorrhagia, and another 30-year-old male patient from family B was characterized with hematoma in the lower extremity. Both patients showed severely decreased FVIII:C, VWF:Ag. Recurrent homozygous VWF c.4696C>T (p.Arg1566Ter) nonsense mutation was identified in the female patient, and novel homozygous VWF c.6450C>A (p.Cys2150Ter) nonsense mutation was identified the male patient. Heterozygotes in family members showed mild/moderate decrease in VWF:Ag or VWF:RCo.

CONCLUSIONS

We identified VWD type 3 in two consanguineous marriage families, and our work further strengthen the risk of delivering disorders inherited in AR manner in populations with frequent consanguineous partnerships.

Impact of low volume citrate tubes on results of first-line hemostasis testing

INTRODUCTION

Pediatric tubes are increasingly used for drawing blood for hemostasis testing. This study has investigated the potential impact of low volume citrate tubes on results of first-line hemostasis testing.

METHODS

The study population comprised 34 patients on warfarin therapy and 17 ostensibly healthy volunteers. Blood was collected into five different evacuated blood tubes from each subject. On right arm, blood was drawn directly into two standard evacuated blood tubes (3-mL Vacuette and 2-mL Vacutest) and one evacuated low volume blood tube (1-mL Vacuette) by straight needle venipuncture. On left arm, blood was drawn using a 5-mL syringe and then transferred within two nonevacuated microtubes (0.5 mL MiniCollect and 0.5 mL Micro Test). Prothrombin time (PT), activated partial thromboplastin time (APTT), and fibrinogen were assayed on ACL TOP 700.

RESULTS

Spearman's correlation of PT, APTT, and fibrinogen values obtained using different tubes was always satisfactory (ie, ≥0.93). A statistically significant bias was frequently found by comparing values obtained in different tubes. Nevertheless, the minimum quality specifications for bias were exceeded only by comparing data of Vacuette 1 mL with those of all other blood tubes for PT, by comparing data of Micro Test 0.5 mL with those of all other blood tubes for APTT, and by comparing data of Micro Test 0.5-mL blood tubes with those of Vacuette 3 mL and Vacuette 1.

CONCLUSION

First-line hemostasis testing using low volume citrate tubes may display differences sometimes exceeding the minimum quality specifications.

Rare forms of von Willebrand disease

von Willebrand disease (VWD) arises from deficiency and/or defect(s) of plasma von Willebrand factor (VWF). In turn, plasma VWF is an adhesive protein which primarily functions by anchoring platelets to regions of vascular injury, thereby assisting prevention of bleeding. There is a proportional reduction also in Factor VIII, due to the absence of the stabilizing and anti-proteolytic effect that VWF normally exerts. VWD is reportedly the most common inherited bleeding disorder and can be classified into quantitative and qualitative defects, with type 1 and 3 VWD respectively identifying partial and total quantitative deficiency of VWF, and type 2 VWD identifying qualitative defects of VWF. The relative incidence of each subtype of VWD differs according to the locality and the ability of clinicians and laboratories to correctly diagnose and classify cases. In general, type 1 VWD is considered the most common type of VWD, whereas types 2 and 3 represent rarer forms. However, in developing countries, and partly because of consanguinity, type 3 VWD is over-represented. This review primarily focuses on the rarer forms of VWD, which typically comprise types 2 (A, B, M and N) and 3 VWD. The review also mentions type 1 VWD, largely for completeness and comparability, and since purportedly "severe" type 1 VWD, albeit not a formally recognized subtype of type 1 VWD, would represent a relatively "rare" form of VWD.

Postanalytical considerations that may improve the diagnosis or exclusion of haemophilia and von Willebrand disease

von Willebrand disease (VWD) and haemophilia represent the most common inherited or acquired bleeding disorders. However, many laboratories and clinicians may be challenged by their accurate diagnosis or exclusion. Difficulties in diagnosis/exclusion may include analytical issues, where assays occasionally generate an incorrect result (ie representing an analytical error) or have limitations in their measurement range of and/or low analytical sensitivity. Also increasingly recognized is the influence of preanalytical issues on the diagnosis of VWD or haemophilia. Unfortunately, postanalytical considerations are often not well considered in the diagnostic process. Therefore, this narrative review aims to provide an overview of some important postanalytical considerations that may help improve the diagnosis of VWD and haemophilia. This review primarily discusses aspects around reporting of test results. However, we also discuss other less well-recognized postanalytical considerations, including the use of assay ratios to help identify differential diagnoses and then guide further investigation.