Showing papers on "Blood Platelet Disorders published in 2009"

Light transmission aggregometry and ATP release for the diagnostic assessment of platelet function.

Abstract: Light transmission aggregometry (LTA) is the gold standard for the study of patients with defects of platelet function. Use of LTA in clinical practice for predicting the risk of thrombosis or monitoring the pharmacologic effects of antiplatelet agents should be discouraged, because not only is the monitoring of treatment with antiplatelet agents (with any laboratory test) not indicated at present, but also the lack of standardization of the technique for LTA makes it additionally unsuitable for this purpose. The need for standardization of LTA has recently been emphasized by the results of four surveys, which showed that there is a wide variation in the methodology used worldwide. A modification of the traditional LTA is the lumiaggregometer, which measures platelet secretion in parallel with platelet aggregation. This technique is probably preferable to traditional LTA in the diagnostic workup of patients with inherited defects of platelet function, because it is more sensitive to the most common disorders, which are characterized by abnormalities of platelet secretion. LTA (or lumiaggregometry) is useful as a first screening test of patients with the clinical suspicion of defects of platelet function because it helps to provide an interim diagnostic hypothesis, which can then be confirmed or discounted using appropriate and specific tests.

Whole blood multiple electrode aggregometry is a reliable point-of-care test of aspirin-induced platelet dysfunction.

Abstract: BACKGROUND:Aspirin is one of the most commonly ingested over-the-counter drugs. In addition to its analgesic and antiinflammatory actions, it also potently inhibits platelet aggregation. Evaluation of aspirin-induced platelet dysfunction is relevant in various clinical situations, including during c

The level of laboratory testing required for diagnosis or exclusion of a platelet function disorder using platelet aggregation and secretion assays.

Abstract: The major advances from research on platelet molecular and cell biology, physiology, and pathophysiology over the past decades have not been adequately translated to clinical laboratory diagnosis. Hereditary platelet function disorders (PFDs) are at least as prevalent in the general population as von Willebrand disease (VWD) although PFDs tend not be as well recognized or evaluated. Clinical mucous and skin bleeding in patients with PFDs is prototypic of primary hemostasis disorders, and the bleeding pattern is not distinguishable from that of other primary hemostasis disorders such as VWD. However, different treatment needs, between these discrete disorders, make a precise diagnosis mandatory. Currently, clinicians receive reliable laboratory reports when testing patients with severe PFDs, such as Glanzmann thrombasthenia and Bernard-Soulier syndrome, due to the distinctive laboratory defects that these disorders present, together with the availability of differential diagnostic tests. This is not the case for the majority of PFDs generically classified as "platelet secretion disorders," which are a heterogeneous group of "mild bleeding disorders," for which there are not universally accepted diagnostic criteria. An important reason for robust diagnostic tests is the high proportion (more than 50% in some reports) of patients with unequivocal bleeding who have no precise diagnosis established after a complete laboratory workup. It is paradoxical that the current "gold standard" test for PFD diagnosis, light transmission aggregometry (LTA), has not been standardized after more than four decades of worldwide clinical use. This review describes current diagnostic assays for PFD in a clinical hemostasis laboratory, relating these with current knowledge on platelet function and pathophysiology. Special emphasis will be given to LTA and platelet secretion tests, as well as to the reasons why sensitive tests are needed to explore the lesser known participation of platelets in blood clotting and fibrinolytic processes.

Diagnosis of mild platelet function disorders. Reliability and usefulness of light transmission platelet aggregation and serotonin secretion assays.

Abstract: Light transmission platelet aggregation (PA), adapted to measure platelet secretion (PS), is the reference test for diagnosing platelet functional disorders (PFD). Problems with these assays include lack of standardisation, unknown reproducibility and lack of universally accepted diagnostic criteria. We addressed these issues in patients with inherited mucocutaneous bleeding (MCB). Normal and abnormal PA tests in 213 patients were reproducible in 93.3% and 90.4% of the cases, respectively. Mean intra-subject coefficient of variation for PA with strong agonists were 0.86 (P or = 42% or irreversible aggregation with 4 micromol/l ADP had 93% and 95% Negative Predictive Value for diagnosing PFD, respectively. PA defects were consistently associated with abnormal PS. In contrast, 14.3% of patients with MCB had isolated PS. Thus, standardized PA/PS assays are highly reproducible and concordant in normal and patient populations. Normal PA with adrenaline and low ADP concentration robustly predict a normal PA. Simultaneous PA/PS assays enable the diagnosis of isolated PS defects. This study confirmed that hereditary PA-PS defects are highly prevalent.

Results of an external proficiency testing exercise on platelet dense-granule deficiency testing by whole mount electron microscopy.

Abstract: Performance on specialized diagnostic tests for platelet disorders, including dense-granule deficiency, is rarely evaluated by external quality assessment (EQA). Members of the North American Specialized Coagulation Laboratory Association that evaluate platelet dense-granule deficiency commonly use whole-mount electron microscopy (EM) methods. This observation led us to develop a pilot EQA survey with standardized EM images and clinical samples on grids from a healthy control subject and a subject with dense-granule deficiency. The survey participants were 8 centers, including 2 with no experience in platelet whole mount EM. All participants, including inexperienced sites, correctly interpreted findings for the normal and dense-granule-deficient platelets. Among experienced sites, agreement was excellent (>82%) on platelet structures to count or not count as dense granules. Participants indicated that future EQA challenges should include clinical samples on grids and standardized images. This is the first report that platelet EM can be assessed by EQA.

Haploinsufficiency of the platelet P2Y12 gene in a family with congenital bleeding diathesis.

Abstract: Two sisters with inherited, severe platelet dysfunction associated with P2Y12 deficiency displayed a single base pair deletion in their P2Y12 genes (378delC), resulting in a frame-shift and premature truncation of the protein. GL, the son of one of them, displayed mild platelet dysfunction and normal P2Y12 sequence. We hypothesized that the abnormal platelet phenotype of GL is due to haploinsufficiency of his P2Y12 gene. We analyzed genomic DNA from the family by Southern Blotting and real-time (RT) PCR. Southern Blotting results demonstrated that GL has a single P2Y12 allele, inherited from his father. RT-PCR revealed that GL, his mother and aunt have one single intact P2Y12 allele, while his father has two P2Y12 alleles. The single GL P2Y12 allele contains normal sequence, while his mother and aunt have the 378delC allele. The results of this study support our hypothesis and illustrate the platelet phenotype associated with P2Y12 haploinsufficiency.

The use of recombinant activated factor VII in platelet disorders: a critical review of the literature

Abstract: Recombinant activated factor VII (rFVIIa, NovoSeven® , Novo Nordisk, Bagsvaerd, Denmark) is a haemostatic agent that was originally developed for the treatment of haemophiliacs with inhibitors and then used successfully for treating haemorrhages in patients with acquired haemophilia1–4. In the last few years, rFVIIa has also been used with benefit as a “universal haemostatic agent” in many other non-haemophilic bleeding situations including congenital factor VII deficiencies, hepatic failure, liver transplantation, surgery and trauma5–7. The haemostatic effect of pharmacological doses of rFVIIa seems to be that of enhancing the rate of thrombin generation on thrombin-activated platelet surfaces, thus providing the thrombin necessary for the formation of a stable fibrin haemostatic plug8. Based on this information, rFVIIa has also been employed in disorders characterised by impaired thrombin generation, such as quantitative and qualitative platelet defects9. Figure 1 illustrates the mechanisms of action of rFVIIa. Figure 1 Mechanisms of action of rFVIIa The current clinical experience regarding the use of rFVIIa for the treatment of bleeding in patients with congenital or acquired platelet disorders is analysed briefly in this review.

Pseudo grey platelet syndrome — Grey platelets due to degranulation in blood collected into EDTA

Abstract: We have studied a woman with a history of mild bruising and bleeding, with a normal platelet count and normal clotting factors, who had platelets that appeared grey when stained and viewed under the microscope. Unlike the grey platelet syndrome, the abnormality was only evident when blood had been collected into EDTA and not when citrate or heparin was used as anticoagulant. This 'pseudo grey platelet syndrome' was associated with platelet dense body and alpha granule secretion with no aggregation and occurred on removal of extracellular Ca2+. We discovered that a plasma factor was responsible which could be an immunoglobulin but which is clearly different from the EDTA-sensitive antibodies which cause platelet aggregation and agglutination. We were not able to demonstrate a relationship between the mild bleeding tendency and the in vitro abnormality.

Thrombophilic patterns of coagulation factors in lupus.

Abstract: Our aim was to better define the coagulation abnormalities in patients with systemic lupus erythematosus who had thrombosis or high-risk clinical settings for thrombosis. Clinical and laboratory data of 111 patients with lupus referred for coagulation assessment because of thrombosis, pregnancy loss or high-risk clinical settings for thrombosis were reviewed retrospectively. Increased activity of procoagulant factors and decreased activity of anti-coagulant factors were observed well above the expected 5% prevalence. All comparisons were significant at the P < 0.001 level. Anticardiolipin antibodies were present in 70.5% of patients tested (55/78) in this high-risk group, but usually in low titres. Platelet hyperfunction was detected in the majority of patients tested (85.7%, 78/91). Hypercoagulability in lupus is complex and is better defined by assessing multiple haemostatic factors in addition to platelet function. Platelet hyperfunction contributes significantly to thrombophilia in lupus and this is the key finding of our study.

Investigation of patients with mild thrombasthenia--a haemorrhagic disorder with prolonged bleeding time probably due to a primary platelet defect.

Abstract: Fifteen families with a haemorrhagic disorder are reported. The patients had a bleeding tendency characterized by easy bruisability, nose bleeding, menorrhagia and bleeding after tooth extractions, accidents or surgery. Laboratory investigation showed prolonged Ivy bleeding time and usually decreased platelet adhesiveness, as measured by Hellem's whole blood method, Salzman's method and occasionally Hellem's plasma-ADP method. Factor VIII and other coagulation factors were normal. The prothrombin consumption test was mostly normal and there was no pathologic fibrinolysis. The inheritance was probably dominant, but the penetrance weak. The disease was probably caused by a primary platelet defect, especially since a similar syndrome was found among relatives of a family with severe thrombasthenia of Glanzmann's type. We call the condition mild thrombasthenia.

A Syndrome of Factor VII Deficiency and Abnormal Platelet Release Reaction

Abstract: A 15-year-old girl with severe factor VII deficiency and chronic arthropathy showed an excessively prolonged bleeding time. Further studies demonstrated low platelet adhesiveness and abnormal platelet aggregation with ADP, collagen and epinephrine. Release of 14C-serotonin was deficient after aggregation with ADP and epinephrine, but was normal with thrombin. Transfusion of plasma or prothrombin complex concentrate resulted in a partial or complete correction of the bleeding time, respectively, but had no effect on in vitro platelet function tests. Both parents and the only sister had factor VII activities of 42%-72% and factor VII antigen levels of 45%-66% of normal and may thus be heterozygotes with respect to factor VII deficiency. All three had normal bleeding times in spite of abnormal in vitro platelet functions. The observations are interpreted to mean that in this family with factor VII deficiency and abnormal platelet release reaction the platelet abnormality as such was not sufficiently severe to prolong the bleeding time unless the factor VII activity was also very low.

Neuropeptide y (npy) as a tumor marker

Abstract: To the Editor: In a recent prospective study by Kogner et al. (1) neuropeptide Y -like immunoreactivity (NPY-LI) was found significantly elevated in plasma from children with B-cell precursor leukemia, whereas children with B-cell, T-cell or myeoloid leukemia had normal plasma levels. Their findings of a consistent and rapid normalization of P-NPY-LI after initiation of chemotherapy implied a tumoral origin of NPY-LI. This was further supported by Northern blot technique showing high levels of NPY mRNA in bone marrow and peripheral lymphoblasts from children with B-cell precursor ALL. In bone marrows from rats, Ericsson et al. (2, 3) demonstrated high concentrations of NPY mRNA and NPY-LI in megakaryocytes and platelets. In particular, high levels of NPY mRNA were found in bone marrow of certain strains of autoimmune mice that develop B-cell lymphoproliferative disorders (2). For these reasons, we have analyzed sera from pa-