Predicting Pulmonary Embolism in Total Joint Arthroplasty Patients A Pilot Study.

Postoperative venous thromboembolism (VTE) is a common and costly complication following total joint arthroplasty (TJA). Development of a refined thrombophilic screening panel will better equip clinicians to identify patients at high-est risk for developing VTEs. In this pilot study, 62 high-risk TJA recipients who had developed pulmonary emboli (PE) within 90-days of surgery were eligible to participate.

Hemophilia A: Emicizumab monitoring and impact on coagulation testing.

Hemophilia A is an X-linked recessive bleeding disorder characterized by absent or ineffective coagulation factor VIII, a condition that could result in a severe and potentially life-threatening bleed. Although the current standard of care involves prophylactic replacement therapy of factor VIII, the development of neutralizing anti-factor VIII alloantibody inhibitors often complicates such therapeutic treatment. Emicizumab (Hemlibra®), a novel recombinant therapeutic agent for patients with hemophilia A, is a humanized asymmetric bispecific IgG4 monoclonal antibody designed to mimic activated factor VIII by bridging factor IXa and factor X thus effecting hemostasis.

Analysis of platelets by flow cytometry in patients with Paroxysmal Nocturnal Hemoglobinuria (PNH).

The marked pro-thrombotic tendency in PNH is likely to be at least partly due to the population of platelets derived from the abnormal stem cell clone. However, identification of GPI (-) platelets by flow cytometry can be technically difficult. Here we describe a technique that involves the addition of aspirin immediately after the separation of platelet rich plasma and the use of gel filtration to isolate platelets away from plasma proteins and other blood cells.

Circulating monocyte-platelet aggregates are a robust marker of platelet activity in cardiovascular disease.

Background And Aims: Platelets are a major culprit in the pathogenesis of cardiovascular disease (CVD). Circulating monocyte-platelet aggregates (MPA) represent the crossroads between atherothrombosis and inflammation. However, there is little understanding of the platelets and monocytes that comprise MPA and the prevalence of MPA in different CVD phenotypes.

Reproducibility over time and effect of low-dose aspirin on soluble P-selectin and soluble CD40 ligand.

Platelet markers [soluble CD40 ligand (sCD40L) and soluble p selectin (sPselectin)] are associated with platelet activation and cardiovascular events. We sought to investigate the reproducibility of these markers over time and the effect of low-dose aspirin on sCD40L and sPselectin in plasma and serum. Following an overnight fast, 40 healthy volunteers had weekly phlebotomy and were administered aspirin 81 mg/day between weeks 3 and 4.

Platelet aggregation and coagulation factors in orthopedic surgery.

Hemostasis is a major concern during the perioperative period. Changes in platelet aggregation and coagulation factors may contribute to the delicate balance between thrombosis and bleeding. We sought to better understand perioperative hemostasis by investigating the changes in platelet aggregation and coagulation factors during the perioperative period.

Mean platelet volume reproducibility and association with platelet activity and anti-platelet therapy.

Some studies suggest that mean platelet volume (MPV) correlates with increased risk for cardiovascular morbidity and mortality. In this study, we aim to assess reproducibility, need for standardized measurements, effect of aspirin, and association with other established markers of platelet activity. Following an overnight fast, 48 healthy volunteers had weekly assessment of platelet activity and were administered aspirin 81 mg daily for 7 d between weeks 3 and 4.

Aspirin attenuates platelet activation and immune activation in HIV-1-infected subjects on antiretroviral therapy: a pilot study.

Background: Mechanisms for increased cardiovascular risk in HIV-1-infected adults are incompletely understood, but platelet activation and immune activation leading to a prothrombotic state have been proposed as significant contributors. Aspirin has antiplatelet and immunomodulatory properties. We explored whether 1 week of low-dose aspirin attenuates platelet activation and immune activation in HIV-1-infected and virologically suppressed adults on antiretroviral therapy.

A new α1-globin mutation, Hb Brugg [α20(B1)His→Gln].

A 2½-year-old male child and a 23-year-old woman with no clinical symptoms were investigated during routine consultations. Cation exchange high performance liquid chromatography (HPLC) revealed an additional peak eluting before Hb A. DNA sequencing showed a novel heterozygous mutation at codon 20 of the α1-globin gene.

The inhibition effect of anti-GPIIIa49-66 antibody on megakaryocyte differentiation.

We previously reported that patients with early-onset HIV-1 ITP developed a unique anti-platelet integrin GPIIIa antibody against the GPIIIa49-66 epitope. Anti-GPIIIa49-66 antibody-induced platelet fragmentation requires sequential activation of the platelet 12-lipoxygenase (12-LO) and NADPH oxidase to release reactive oxygen species (ROS). 12-LO is upstream of the NADPH oxidase pathway and 12(S)-HETE, the product of 12-LO, induces the same oxidative platelet fragmentation as anti-GPIIIa49-66.

Specific cross-reaction of anti-dsDNA antibody with platelet integrin GPIIIa49-66.

Anti-platelet autoantibodies are frequently found in systemic lupus erythematosus (SLE) patients and contribute to the development of SLE-associated immunologic thrombocytopenia (SLE-ITP). Although the correlation of anti-dsDNA autoantibody with platelet-associated antibody has been reported, the potential mechanism underlying such a correlation is incompletely understood. We have reported that anti-platelet integrin GPIIIa49-66 (CAPESIEFPVSEARVLED) autoantibodies play a major role in the development of HIV-1-related thrombocytopenia (HIV-1-ITP).

Dissolution of arterial platelet thrombi in vivo with a bifunctional platelet GPIIIa49-66 ligand which specifically targets the platelet thrombus.

Patients with HIV-1 immune-related thrombocytopenia have a unique antibody (Ab) against integrin GPIIIa49-66 capable of inducing oxidative platelet fragmentation via Ab activation of platelet nicotinamide adenine dinucleotide phosphate oxidase and 12-lipoxygenase releasing reactive oxygen species. Using a phage display single-chain antibody (scFv) library, we developed a novel human monoclonal scFv Ab against GPIIIa49-66 (named A11) capable of inducing fragmentation of activated platelets. In this study, we investigated the in vivo use of A11.

Clinical and molecular genetic analysis of a family with macrothrombocytopenia and early onset sensorineural hearing loss.

A kindred with inherited macrothrombocytopenia (MTCP) and sensorineural hearing loss (SNHL) from Ghent, Belgium was identified. Currently, joint expression of MTCP and hearing loss are linked to mutations within MYH9 only. Thus, we tested the hypothesis that a mutation within MYH9 is responsible for the autosomal dominant inheritance of MTCP and hearing loss in the Ghent family.

C-terminal ADAMTS-18 fragment induces oxidative platelet fragmentation, dissolves platelet aggregates, and protects against carotid artery occlusion and cerebral stroke.

Anti-platelet integrin GPIIIa49-66 antibody (Ab) induces complement-independent platelet oxidative fragmentation and death by generation of platelet peroxide following NADPH oxidase activation. A C-terminal 385-amino acid fragment of ADAMTS-18 (a disintegrin metalloproteinase with thrombospondin motifs produced in endothelial cells) induces oxidative platelet fragmentation in an identical kinetic fashion as anti-GPIIIa49-66 Ab. Endothelial cell ADAMTS-18 secretion is enhanced by thrombin and activated by thrombin cleavage to fragment platelets.

Role of molecular mimicry of hepatitis C virus protein with platelet GPIIIa in hepatitis C-related immunologic thrombocytopenia.

Patients with HIV-1 immune-related thrombocytopenia (HIV-1-ITP) have a unique Ab against platelet GPIIIa49-66 capable of inducing oxidative platelet fragmentation in the absence of complement. HIV-1-seropositive drug abusers are more prone to develop immune thrombocytopenia than non-drug abusers and have a higher coinfection with hepatitis C virus (HCV) than non-drug abusers (90% vs 30%). Molecular mimicry was sought by screening a phage peptide library with anti-GPIIIa49-66 antibody as bait for peptides sharing homology sequences with HCV.

Platelet fragmentation requires a specific structural conformation of human monoclonal antibody against beta3 integrin.

We have described an autoantibody against beta3 (GPIIIa49-66), a region of platelet integrin alphaIIbbeta3 that is unique. It induces platelet fragmentation in the absence of complement via antibody activation of platelet NADPH oxidase and 12-lipoxygenase to release reactive oxygen species, which destroy platelets. To study the mechanism of anti-GPIIIa antibody-induced platelet fragmentation, we screened a human single chain Fv antibody library with the GPIIIa49-66 peptide.

Platelet particle formation by anti GPIIIa49-66 Ab, Ca2+ ionophore A23187, and phorbol myristate acetate is induced by reactive oxygen species and inhibited by dexamethasone blockade of platelet phospholipase A2, 12-lipoxygenase, and NADPH oxidase.

An HIV antibody (Ab) against platelet integrin GPIIIa49-66 induces complement-independent platelet particle formation by the elaboration of reactive oxygen species (ROS) downstream of the activation of the platelet NADPH oxidase by the 12-lipoxygenase (12-LO) product 12(S)-HETE. To determine whether other inducers of platelet particle formation also function via the induction of ROS, we examined the effects of the Ca(2+) ionophore A23187 and phorbol myristate acetate (PMA). Both agents induced oxidative platelet particle formation in an identical fashion as Ab, requiring Ca(2+) flux and 12(S)-HETE production as well as intact NADPH oxidase and 12-LO pathways.

Role of molecular mimicry to HIV-1 peptides in HIV-1-related immunologic thrombocytopenia.

Patients with early HIV-1 infection develop an autoimmune thrombocytopenia in which antibody is directed against an immunodominant epitope of the beta3 (glycoprotein IIIa [GPIIIa]) integrin, GPIIIa49-66. This antibody induces thrombocytopenia by a novel complement-independent mechanism in which platelets are fragmented by antibody-induced generation of H2O2 derived from the interaction of platelet nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and 12-lipoxygenase. To examine whether sharing of epitope between host and parasite may be responsible for this immunodominant epitope, we screened for antibody-reactive peptides capable of inhibiting platelet lysis and oxidation in vitro, using a filamentous phage display 7-mer peptide library.

HPLC retention time as a diagnostic tool for hemoglobin variants and hemoglobinopathies: a study of 60000 samples in a clinical diagnostic laboratory.

Background: Previous evaluations of HPLC as a tool for detection of hemoglobin variants have done so within newborn-screening programs and/or by use of stored samples. We describe a 32-month prospective study in a clinical diagnostic laboratory in which we evaluated the imprecision of HPLC retention times and determined the retention times for hemoglobin variants seen in a multiethnic setting.

Methods: We analyzed all samples on the Bio-Rad Variant II HPLC system.

Complement-independent Ab-induced peroxide lysis of platelets requires 12-lipoxygenase and a platelet NADPH oxidase pathway.

Antiplatelet GPIIIa49-66 Ab of HIV-related thrombocytopenic patients induces thrombocytopenia and platelet fragmentation by the generation of peroxide and other reactive oxygen species (ROS). Here we report the presence of a functional platelet NADPH oxidase pathway that requires activation by the platelet 12-lipoxygenase (12-LO) pathway to fragment platelets. A new Ab-mediated mechanism is described in which the platelet 12-LO product, 12(S)-HETE activates the NADPH oxidase pathway to generate ROS.

Hemoglobin C and hemoglobin O-Arab variants can be diagnosed using the Bio-Rad Variant II high-performance liquid chromatography system without further confirmatory tests.

Context: Current standards for laboratory accreditation from the College of American Pathologists state that when high-performance liquid chromatography (HPLC) is used as a screening test, all non-A, non-S abnormal hemoglobin (Hb) variants must be confirmed by an alternative method, including alkaline and acid electrophoresis.

Objective: To determine whether confirmation of Hb C and Hb O-Arab variants by an alternative method is required when using the Bio-Rad Variant II HPLC system.

Design: We reviewed 48 478 consecutive hemoglobin identification test results performed on the Bio-Rad Variant II HPLC system during the period November 15, 2000 to January 15, 2003.