[Show abstract][Hide abstract] ABSTRACT: Although rare, the prevalence of inherited platelet function disorders (IPFD) is probably underestimated due to underdiagnosis . IPFD are heterogeneous in severity, mechanisms, and frequency and few are characterized at the molecular level. While severe IPFD, like Glanzmann Thrombasthenia (GT) or Bernard-Soulier Syndrome (BSS), are now rather straightforward to identify, the diagnosis of most other forms is cumbersome and requires complex assaysThis article is protected by copyright. All rights reserved.
Journal of Thrombosis and Haemostasis 11/2014; 13(2). DOI:10.1111/jth.12792 · 5.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: IntroductionThe development of an automated, von Willebrand factor (VWF) activity assay, Innovance® VWF Ac (VWF:Ac), which measures VWF binding to the platelet receptor glycoprotein Ibα without ristocetin, led us to evaluate the assay for diagnosing von Willebrand disease (VWD) and monitoring therapy.Methods
After validating that the assay could be performed on an instrument from a different manufacturer, we compared VWF:Ac to VWF ristocetin cofactor activity (VWF:RCo) findings, including ratios of activity/antigen, for 100 healthy controls and 262 consecutive clinical samples from 217 patients (197 adults, 64 children, n = 1 age unknown) referred for VWF testing.ResultsThere was excellent correlation (R2 = 0.96) between VWF:Ac results run at two different sites on two different instruments. VWF:Ac had greater precision and sensitivity to low levels of VWF than the VWF:RCo method. Although there was good correlation between VWF:Ac and VWF:RCo results among healthy controls and patient subjects, VWF:Ac results were undetectable and/or significantly lower than VWF:RCo among patients who had types 2A, 2B, or 2M VWD. Additionally, a higher proportion of patient samples were classified as showing qualitative defects using the VWF:Ac compared with VWF:RCo method. While most samples drawn on VWD therapy had similar VWF levels by VWF:Ac and VWF:RCo, a type 2B VWD subject on replacement had much lower activity estimated by VWF:Ac.Conclusion
We conclude that Innovance® VWF Ac is suitable for the diagnosis, classification, and monitoring of VWD, and that it has a number of advantages over VWF:RCo method.
International journal of laboratory hematology 06/2014; 36(3). DOI:10.1111/ijlh.12218 · 1.82 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Diagnostic tests for von Willebrand disease (VWD) are important for the assessment of VWD, which is a commonly encountered bleeding disorder worldwide. Technical innovations have been applied to improve the precision and lower limit of detection of von Willebrand factor (VWF) assays, including the ristocetin cofactor activity assay (VWF:RCo) that uses the antibiotic ristocetin to induce plasma VWF binding to glycoprotein (GP) IbIXV on target platelets. VWF-collagen-binding assays, depending on the type of collagen used, can improve the detection of forms of VWD with high molecular weight VWF multimer loss, although the best method is debatable. A number of innovations have been applied to VWF:RCo (which is commonly performed on an aggregometer), including replacing the target platelets with immobilized GPIbα, and quantification by an enzyme-linked immunosorbent assay (ELISA), immunoturbidimetric, or chemiluminescent end-point. Some common polymorphisms in the VWF gene that do not cause bleeding are associated with falsely low VWF activity by ristocetin-dependent methods. To overcome the need for ristocetin, some new VWF activity assays use gain-of-function GPIbα mutants that bind VWF without the need for ristocetin, with an improved precision and lower limit of detection than measuring VWF:RCo by aggregometry. ELISA of VWF binding to mutated GPIbα shows promise as a method to identify gain-of-function defects from type 2B VWD. The performance characteristics of many new VWF activity assays suggest that the detection of VWD, and monitoring of VWD therapy, by clinical laboratories could be improved through adopting newer generation VWF assays.
International journal of laboratory hematology 06/2014; 36(3). DOI:10.1111/ijlh.12220 · 1.82 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background
Diagnosis of inherited platelet function disorders (IPFD) is important for appropriate management, and to improve epidemiologic and clinical knowledge. However, there is still a lack of consensus on the diagnostic approach.Objectives
To gain knowledge on the current practices for the diagnosis of IPFD worldwide.MethodsA 67 item questionnaire was distributed to the ISTH members and to the members of several hemostasis and thrombosis national societies.ResultsA total of 202 laboratories from 37 countries participated in the survey. The most frequent criterion to define patients with a suspected IPFD was a history of mucocutaneous bleeding and no acquired cause, but heterogeneity on the identification criteria was evident. Only 64.5% of respondents performed a direct clinical interview. On average, each laboratory studied 72 patients/year. The most commonly used laboratory equipments were the light-transmission aggregometer (LTA), the platelet function analyzer-100 (PFA-100®), and flow-cytometer. Screening tests were platelet count, peripheral blood smear, LTA, PFA-100®. Second step tests were flow-cytometry, molecular genetic analysis and electron microscopy. Methodologies used varied widely. In total, around 14,000 patients were investigated yearly and 60% turned out not to have a defect. Of the remaining 40%, only 8.7% received a diagnosis at a molecular level.Conclusions
Many laboratories worldwide are involved in the diagnosis of IPFD. A large fraction of the patients studied remain without a diagnosis. A high variability in the diagnostic approaches is evident.This article is protected by copyright. All rights reserved.
Journal of Thrombosis and Haemostasis 06/2014; 12(9). DOI:10.1111/jth.12650 · 5.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We analyzed results from the External quality Control of diagnostic Assays and Tests program to assess current clinical laboratory practice and performance of different methods for factor XIII (FXIII) testing internationally. FXIII proficiency testing data from all eight surveys conducted in 2010 and 2011 were analyzed (1,283 results), comparing the three available methods for detecting FXIII deficiency, thus including clot-solubility qualitative activity, quantitative activity, and antigen. Clot-solubility qualitative assays detected a deficiency in only 16% (11/69) of samples with less than 2% FXIII. Assays using added thrombin detected more deficiencies (33%) than did assays without added thrombin (11%). The most commonly used quantitative activity method tended to produce higher results for low FXIII samples than other quantitative activity methods. Antigen results generally showed good accuracy compared with expected levels. The mean interlaboratory coefficients of variation showed wide variability, especially for samples with less than 10% FXIII activity. Laboratory self-classification of results (as normal vs. abnormal) was good, and was slightly better for specimens with ≤ 25% FXIII than for specimens with 26 to ≥ 70% FXIII. We conclude that quantitative activity assays perform better for detecting FXIII deficiency than clot solubility assays, although some quantitative activity assays overestimate low FXIII levels.
Seminars in Thrombosis and Hemostasis 02/2014; 40(2). DOI:10.1055/s-0034-1365841 · 3.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Light transmission aggregometry (LTA) is the most common method used to assess platelet function. However, there is no universal standard for its performance. The Platelet Physiology Subcommittee of the Scientific and Standardization Committee (SSC) of the International Society on Thrombosis and Haemostasis formed a working party of experts with the aim of producing a series of consensus recommendations for standardizing LTA. Due to a lack of investigations that directly compared different methodologies to perform LTA studies, there were insufficient data to develop evidence-based guidelines. Therefore, the RAND method was used, which obtains a formal consensus among experts about the appropriateness of health care interventions, particularly when scientific evidence is absent, scarce and/or heterogeneous. Using this approach, each expert scored as "appropriate", "uncertain" or "inappropriate" a series of statements about the practice of LTA, which included pre-analytical variables, blood collection, blood processing, methodological details, choice of agonists and the evaluation and reporting of results. After presentation and public discussion at SSC meetings, the assessments were further refined to produce final consensus recommendations. Before delivering the recommendations, a formal literature review was performed using a series of defined search terms about LTA. Of the 1830 potentially relevant studies identified, only 14 publications were considered to be actually relevant for review. Based upon the additional information, 6 consensus statements were slightly modified. The final statements were presented and discussed at the SSC Meeting in Cairo (2010) and formed the basis of a consensus document, which is the subject of the present report. This article is protected by copyright. All rights reserved.
Journal of Thrombosis and Haemostasis 04/2013; 11(6). DOI:10.1111/jth.12231 · 5.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Laboratory testing is essential for diagnosing bleeding disorders. The tests and panels that laboratories currently use for bleeding disorder evaluation are not standardized, although most offer coagulation screening tests in bleeding disorder panels. Some tests for bleeding disorders, including von Willebrand factor multimer assays and tests for rarer disorders, are not widely available. Accordingly, clinicians and laboratories need tailored strategies for evaluating common and rare bleeding disorders. Coagulation screening tests have high specificity, however, false positives and false negatives do occur among subjects evaluated for bleeding disorders and more specific tests (e.g., factor assays) are required to further assess abnormalities. Tests for defects in primary hemostasis have similar high specificity but much greater sensitivity for common bleeding disorders than coagulation screening tests. Nonetheless, extensive testing fails to establish a diagnosis in a significant number of individuals considered to have significant bleeding problems. Rare bleeding disorder investigations are important to diagnose some conditions, particularly those with delayed-onset bleeding, such as factor XIII deficiency, α2 antiplasmin deficiency, plasminogen activator inhibitor-1 deficiency, and Quebec platelet disorder. These issues need careful consideration when assessing patients for congenital and acquired bleeding problems.
International journal of laboratory hematology 03/2013; 35(3). DOI:10.1111/ijlh.12077 · 1.82 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Hematology laboratories have a vital role in providing diagnostic testing for a wide range of blood disorders. Improvements in hematology laboratory diagnostics are highly dependent on new discoveries on blood disorder pathology, the translation of new knowledge into assays for clinical testing purposes, and research that assesses, compares, and optimizes diagnostic practices. This article reviews the author's experiences with research leading to improved blood disorder diagnosis, including research studies on Quebec platelet disorder and other bleeding disorders, evaluations of practice, and research on the external quality assessment of diagnostic testing for platelet function disorders. The importance of research to advancing diagnostic testing for blood disorders is emphasized.
International journal of laboratory hematology 03/2013; 35(3). DOI:10.1111/ijlh.12074 · 1.82 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Genetic investigations have led to important advances in our knowledge of genes, proteins, and microRNA that influence circulating platelet counts, platelet size, and function. The application of genome-wide association studies (GWAS) to platelet traits has identified multiple loci with a significant association to platelet number, size, and function in aggregation and granule secretion assays. Moreover, the genes altered by disease-causing mutations have now been identified for several platelet disorders, including X-linked recessive, autosomal dominant, and autosomal recessive platelet disorders. Some mutations that cause inherited platelet disorders involve genes that GWAS have associated to platelet traits. Although disease-causing mutations in many rare and syndromic causes of platelet disorders have now been characterized, the genetic mutations that cause common inherited platelet disorders, and impair platelet aggregation and granule secretion, are largely unknown. This review summarizes current knowledge on the genetic loci that influence platelet traits, including the genes with well-characterized mutations in certain inherited platelet disorders.
Seminars in Thrombosis and Hemostasis 03/2013; 39(3). DOI:10.1055/s-0033-1334466 · 3.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Bleeding disorder panels often include the prothrombin time (PT)/international normalized ratio (INR), activated partial thromboplastin time (APTT), fibrinogen level, and thrombin time (TT). We explored the detection of abnormalities from bleeding disorders by these tests among subjects referred for bleeding disorder assessments, using data from a bleeding disorder study to determine sensitivities and specificities. Among subjects referred to hematologists for bleeding disorder assessment, coagulation defects were uncommon and the APTT and TT detected many nonsignificant abnormalities. While all test and panel specificities were acceptable (88 to 100%), coagulation screening tests were less sensitive to clinically significant abnormalities (1.0 to 2.1%) than von Willebrand disease (VWD) screens (6.7%), and light transmission platelet aggregometry (LTA) (26%). Accordingly, panels comprising PT/INR, APTT, fibrinogen, and TT had lower sensitivity to bleeding disorders (3.7%) than panels expanded to include VWD screens (8.5%), or VWD screens and LTA (30%). These findings have important implications for bleeding disorder diagnosis.
Seminars in Thrombosis and Hemostasis 09/2012; 38(7):742-52. DOI:10.1055/s-0032-1326780 · 3.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The evaluation of the coagulation profile has used so far either clotting-based or chromogenic assays with different endpoints. Clotting-based techniques are the most used worldwide, and they certainly are useful for diagnosis of clotting factor deficiencies. However, the information provided is relatively limited, and therefore the individual profile of coagulation is poorly assessed. This is reflected by the weak correlation between the results of these assays and the clinical phenotype. Among the assays that benefited from technological advances, thrombin generation and thromboelastography are probably the most actively investigated, but they require specific instruments and are not fully automated. Their standardisation level is rapidly progressing, and they are progressively entering the clinical scene, with the attempt to provide additional information on the coagulation process and a meaningful clinical correlation. These inherited bleeding disorders frequently require replacement therapy using clotting factor concentrates that increase the plasma level of the missing clotting factor. The classical adjustment of the therapy is mainly based on the measurement of the plasma clotting activity of the protein administered. If one considers that a certain level of thrombin generated would predict clinical efficacy, monitoring of thrombin formation might offer new possibilities to individually predict the bleeding phenotype, select the most adapted therapeutic product and tailor the dose. The same holds true for thromboelastography/thromboelastometry which evaluate fibrin formation as well as clot resistance to fibrinolytic challenge, one step further down in the coagulation process. In this regard, these 2 assays could be seen as complementary in terms of information provided on the coagulation profile at the individual level.
[Show abstract][Hide abstract] ABSTRACT: The quality of platelet aggregation and dense granule deficiency testing is important for diagnosing platelet function disorders. After a successful pilot exercise on diagnosing platelet dense granule deficiency by electron microscopy (EM), the North American Specialized Coagulation Laboratory Association (NASCOLA) has launched regular external quality assurance (EQA) for dense granule EM, as well as for the interpretation of platelet aggregation findings. EQA records were analyzed to assess performance. For EM EQA, between 2009 and 2011, there was excellent performance in distinguishing normal from dense granule-deficient samples and good (>70%) agreement on classifying most electron dense structures in platelets. For aggregation EQA, some normal variants were misclassified and overall case interpretations were more acceptable for rare disorders than for common findings. NASCOLA experiences with these EQAs indicate that there is a need to improve the quality of platelet disorder evaluations. For aggregometry interpretations, deficits in performance could be addressed by translating guideline recommendations into practice.
Seminars in Thrombosis and Hemostasis 06/2012; 38(6):622-31. DOI:10.1055/s-0032-1319767 · 3.88 Impact Factor