Viscoelastic testing in pediatric patients.

A tailored transfusion algorithm based on viscoelastic testing in the perioperative period or in trauma patients is recommended by guidelines for bleeding management. Bleeding management strategies in neonates and children are mostly extrapolated from the adult experience, as published evidence in the youngest age group is scarce. This manuscript is intended to give a structured overview of what has been published on the use of viscoelastic testing to guide bleeding management in neonates and children. Several devices that use either the traditional viscoelastic method or resonance viscoelastography technology are on the market. Reference ranges for children have been evaluated in only some of them. As most of the hemostasis maturation processes can be observed during the first year of life, adult reference ranges for viscoelastic testing could be applied over the age of 1 year. The majority of the published trials in children are based on retrospective analyses describing the correlation between viscoelastic testing and standard laboratory testing or focusing on the prediction of bleeding. Clinically more relevant studies in pediatric patients undergoing cardiac surgery have demonstrated that the implementation of a transfusion algorithm based on viscoelastic testing has significantly reduced transfusion requirements and that this approach has enabled a rapid detection of coagulation disorders in the presence of excessive bleeding. Although further studies are urgently needed, experts have reviewed the use of a transfusion algorithm based on viscoelastic testing in children as a feasible approach, as it has been shown to improve bleeding management and rationalize blood product transfusion.

Fibrinogen concentrates in hereditary fibrinogen disorders: Past, present and future.

Hereditary fibrinogen disorders (HFD) are rare coagulation disorders. Even if the spectrum of symptoms is broad depending on the sub-type, bleeding is the most common complication. Of the available sources of fibrinogen replacement, fibrinogen concentrate provides a safer and more effective option to treat and prevent bleeding. Recent clinical trials on established and new fibrinogen concentrates have increased our knowledge on the clinical pharmacology of these products, pointing out possible age and weight differences for dose adjustment. The efficacy of fibrinogen infusions has been demonstrated, especially for the management of acute bleeding with an excellent response based on investigator rating. The target fibrinogen levels in the setting of both minor and major surgeries have been better specified. The safety has been confirmed with a low number of adverse events but there still remains concern over possible thrombotic risks. Pharmacological, clinical aspects and future perspectives on the utilization of fibrinogen concentrates in the treatment and prevention of bleeding in patients with HFD are reviewed.

Desmopressin acetate (DDAVP) for preventing and treating acute bleeds during pregnancy in women with congenital bleeding disorders.

BACKGROUND: Congenital bleeding disorders can cause obstetric haemorrhage during pregnancy, labour and following delivery. Desmopressin acetate (DDAVP) is found to be an effective drug which can reduce the risk of haemorrhage and can also stop bleeding in certain congenital bleeding disorders. Its use in pregnancy has been controversial. Hence beneficial and adverse effects of DDAVP in these groups of pregnant women should be evaluated.This is an update of a Cochrane Review first published in 2013 and updated in 2015. OBJECTIVES: To evaluate the efficacy and safety of DDAVP in preventing and treating acute bleeding in pregnant women with bleeding disorders. SEARCH METHODS: We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Coaguopathies Trials Register comprising references identified from comprehensive electronic database searches and handsearches of relevant and abstract books of conferences proceedings. We also searched several clinical trial registries and grey literature (27 August 2017).Date of most recent search of the Cochrane Cystic Fibrosis and Genetic Disorders Group's Coaguopathies Trials Register: 01 October 2018. SELECTION CRITERIA: Randomised and quasi-randomised controlled trials investigating the efficacy of DDAVP versus tranexamic acid or factor VIII or rFactor VII or fresh frozen plasma in preventing and treating congenital bleeding disorders during pregnancy were eligible. DATA COLLECTION AND ANALYSIS: No trials matching the selection criteria were eligible for inclusion. MAIN RESULTS: No trials matching the selection criteria were eligible for inclusion. AUTHORS' CONCLUSIONS: No randomised controlled trials were identified investigating the relative effectiveness of DDAVP for bleeding during pregnancy in women with congenital bleeding disorders. In the absence of high-quality evidence, clinicians need to use their clinical judgement and lower level evidence (e.g. from observational trials) to decide whether or not to treat women with congenital bleeding disorders with DDAVP.Given the ethical considerations, future randomised controlled trials are unlikely. However, other high-quality controlled studies (such as risk allocation designs, sequential design, parallel cohort design) to investigate the risks and benefits of using DDAVP in this population are needed.Given that there are unlikely to be any trials published in this area, this review will no longer be regularly updated.

Congenital and acquired bleeding disorders.

Hemostasis can be characterized as an array of physiological mechanisms providing both blood fluidity in the intact blood vessels and hemostasis in the event of impaired continuity of the blood vessel wall. The impaired hemo-static balance may lead on the one hand to an increased tendency to bleed, either spontaneously or only in response to an external stimulus. At the opposite end of bleeding are thrombophilic conditions characterized by an increased tendency to blood coagulation and thereby to the development of venous or arterial thrombosis. The hemostatic balance is the result of normal functioning of the blood vessel wall, platelets and plasma agents which include the coagulation and fibrinolytic systems and their inhibitors. By coagulation we understand the process leading to the formation of fibrin networks including the controlled interaction of coagulation factors. It is a physiological process as opposed to thrombosis which can be defined as increased coagulation under pathological conditions. Key words: coagulation - coagulation factors - coagulopathy - hemophilia - inhibitors of coagulation factors deficiencies - purpura - thrombocytopathy - thrombocytopenia.

Desmopressin acetate (DDAVP) for preventing and treating acute bleeds during pregnancy in women with congenital bleeding disorders.

BACKGROUND: Congenital bleeding disorders can cause obstetric haemorrhage during pregnancy, labour and following delivery. Desmopressin acetate is found to be an effective drug which can reduce the risk of haemorrhage and can also stop bleeding in certain congenital bleeding disorders. Its use in pregnancy has been controversial. Hence beneficial and adverse effects of desmopressin acetate in these groups of pregnant women should be evaluated.This is an update of a Cochrane review first published in 2013. OBJECTIVES: To determine the efficacy of desmopressin acetate in preventing and treating acute bleeds during pregnancy in women with congenital bleeding disorders. SEARCH METHODS: We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Coaguopathies Trials Register comprising references identified from comprehensive electronic database searches and handsearches of relevant and abstract books of conferences proceedings. We also searched for any randomised controlled trials in a registry of ongoing trials and the reference lists of relevant articles and reviews.Date of most recent search: 18 June 2015. SELECTION CRITERIA: Randomised and quasi-randomised controlled trials investigating the efficacy of desmopressin acetate versus tranexamic acid or factor VIII or rFactor VII or fresh frozen plasma in preventing and treating congenital bleeding disorders during pregnancy were eligible. DATA COLLECTION AND ANALYSIS: No trials matching the selection criteria were eligible for inclusion. MAIN RESULTS: No trials matching the selection criteria were eligible for inclusion. AUTHORS' CONCLUSIONS: The review did not identify any randomised controlled trials investigating the relative effectiveness of desmopressin acetate for bleeding during pregnancy in women with congenital bleeding disorders. In the absence of high quality evidence, clinicians need to use their clinical judgement and lower level evidence (e.g. from observational trials) to decide whether or not to treat women with congenital bleeding disorders with desmopressin acetate.Given the ethical considerations, future randomised controlled trials are unlikely. However, other high quality controlled studies (such as risk allocation designs, sequential design, parallel cohort design) to investigate the risks and benefits of using desmopressin acetate in this population are needed.

Inherited, congenital and acquired disorders by hemostasis (vascular, platelet & plasmatic phases) with repercussions in the therapeutic oral sphere.

The hemostasis alterations, either congenital or hereditary origin, and acquired, are circumstances that hinder oral care to patients who suffer them and also generates in the professional who has to attend, high stress. Bleeding control once established and dental treatment planning, both in the aspect of preparation, as the realization of the odonto-stomatological therapeutic, has suffered updates that do need to remember certain aspects of the care of these patients. But we must not forget that the hematologist or internist who controls the patient's medical condition, is a cornerstone for the planning and implementation of treatment plans. We must also remember that, in certain circumstances, treatment should be performed in a hospital setting. In this review, we aim to provide the odonto-stomatologist guidance on how to address the problem and provide simple and updated guidelines to apply in the treatment of these people.

Noninvasive assessment of liver fibrosis in patients with chronic hepatitis C (and congenital bleeding disorders): where do we stand?

The assessment and monitoring of liver fibrosis (LF) is a key issue in the management and definition of prognosis of patients with chronic hepatitis C (CHC). In this respect, despite recognized limitations (invasive nature, sampling errors, interobserver variability, nondynamic evaluation of LF), liver biopsy is traditionally considered the reference standard. These limitations stimulated the search for noninvasive approaches for the assessment of LF, particularly attractive in patients with hemophilia and other congenital bleeding disorders (CBD). In patients with congenital bleeding disorders (CBD), who often suffer from CHC because of the past use of nonvirally inactivated plasma-derived products, the risk of bleeding hamper to routinely obtain histological data for LF staging. A variety of methods have been proposed and, in some cases, validated in patients with CHC and other liver diseases, including biomarkers directly or indirectly associated with LF, often combined in scores or algorithms, and the more recently developed physical approaches, evaluating the properties of the liver parenchyma with instrumental techniques studying the propagation of specific signals, that is, transient elastography (TE), acoustic radiation force impulse imaging elastography, and magnetic resonance elastography. This review will describe the available strategies for noninvasive assessment of LF, with more details on the latter promising instrumental approaches. Moreover, although lacking of validation against liver biopsy, recent studies extending the use of noninvasive methods (particularly TE) in the setting of patients with CBD will be discussed.

Desmopressin acetate (DDAVP) for preventing and treating acute bleeds during pregnancy in women with congenital bleeding disorders.

BACKGROUND: Congenital bleeding disorders can cause obstetric haemorrhage during pregnancy, labour and following delivery. Desmopressin acetate is found to be an effective drug which can reduce the risk of haemorrhage and can also stop bleeding in certain congenital bleeding disorders. Its use in pregnancy has been controversial. Hence beneficial and adverse effects of desmopressin acetate in these groups of pregnant women should be evaluated. OBJECTIVES: To determine the efficacy of desmopressin acetate in preventing and treating acute bleeds during pregnancy in women with congenital bleeding disorders. SEARCH METHODS: We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Coaguopathies Trials Register comprising references identified from comprehensive electronic database searches and handsearches of relevant and abstract books of conferences proceedings. We also searched for any randomised controlled trials in a registry of ongoing trials and the reference lists of relevant articles and reviews.Date of most recent search: 28 February 2013. SELECTION CRITERIA: Randomised and quasi-randomised controlled trials investigating the efficacy of desmopressin acetate versus tranexamic acid or factor VIII or rFactor VII or fresh frozen plasma in preventing and treating congenital bleeding disorders during pregnancy were eligible. DATA COLLECTION AND ANALYSIS: No trials matching the selection criteria were eligible for inclusion. MAIN RESULTS: No trials matching the selection criteria were eligible for inclusion. AUTHORS' CONCLUSIONS: The review did not identify any randomised controlled trials investigating the relative effectiveness of desmopressin acetate for bleeding during pregnancy in women with congenital bleeding disorders. In the absence of high quality evidence, clinicians need to use their clinical judgement and lower level evidence (e.g. from observational trials) to decide whether or not to treat women with congenital bleeding disorders with desmopressin acetate.Given the ethical considerations, future randomised controlled trials are unlikely. However, other high quality controlled studies (such as risk allocation designs, sequential design, parallel cohort design) to investigate the risks and benefits of using desmopressin acetate in this population are needed.

[Specific treatment for intracerebral hemorrhage. Experts' recommendations: stroke management in the intensive care unit]. / Traitement spécifique des hématomes cérébraux. Recommandations formalisées d'experts: prise en charge de l'AVC par le réanimateur.

Spontaneous intracerebral hemorrhages represent from 10 to 15% of strokes. They can be defined by the eruption of arterial blood within the cerebral parenchyma. Clinical signs are not specific and the diagnosis can only be made using brain imaging techniques (CT or magnetic resonance imaging). Management of intracerebral hemorrhage combines general measures (neurovascular intensive care unit, treatment of high blood pressure and of neurotoxic factors) with more specific measures including correction of coagulation abnormalities and, in some cases, neurosurgical treatment.

Guidelines on the laboratory diagnosis of congenital bleeding disorders in Pakistan.

Congenital bleeding disorders are found in all racial groups and are present worldwide. Among all of them haemophilia A, B and Von Willebrand's disease are the commonest and they are characterized by the low blood levels of factor VIII, IX and Von Willebrand's factor respectively. Severity of bleeding is proportional to the severity of factor deficiency. The diagnosis of bleeding disorders can be complex, and no single diagnostic tests are suitable for all patients. The guideline was developed after reviewing relevant publications, summarizing current understanding of bleeding disorders and classification, and present a consensus diagnostic recommendation based on analysis of the literature and expert opinion. They also suggest an approach for clinical and laboratory evaluation of individuals with bleeding symptoms, history of bleeding or conditions associated with increased bleeding risk. The document summarizes needs for improvement in laboratory testing and quality which is very much needed in Pakistan to make a correct diagnosis, train master trainers, identify complications of bleeding disorders in local population, increase awareness among masses, involve government in haemophilia care, education of patients and their families and health care community. It further enhances the need for research in bleeding disorders, including clinical research to obtain more objective information about bleeding symptoms, advancements in diagnostic and therapeutic tools.

Measuring the level of agreement in hematologic and biochemical values between blood sampling sites in leatherback sea turtles (Dermochelys coriacea).

Conservation programs to protect endangered sea turtles are being instituted worldwide. A common practice in these programs is to collect blood to evaluate the health of the turtles. Several different venipuncture sites are used to collect blood from sea turtles for hematologic and biochemistry tests, depending on the species. To date, it is unknown what affect venipuncture site may have on sample results. The purpose of this study was to measure the level of agreement between hematologic and biochemistry values collected from the dorsal cervical sinus and the interdigital vein of leatherback (Dermochelys coriacea) sea turtles. Paired heparinized blood samples were obtained from the dorsal cervical sinus and the interdigital vein of 12 adult female nesting leatherback sea turtles on Keys Beach, St. Kitts, West Indies. Even though the sample population was small, the data for each chemistry were normally distributed, except for creatine kinase (CK). There was no significant difference when comparing biochemistry or hematologic values by venipuncture site, except for CK (P = 0.02). The level of agreement between sampling sites was considered good for albumin, calcium, globulin, glucose, packed cell volume, phosphorus, potassium, sodium, total protein, total solids, uric acid, white blood cell count, and all of the individual white cell types, while the level of agreement for aspartate aminotransferase and CK were considered poor. This information, coupled with the fact that the interdigital vein affords a less-invasive procedure, demonstrates that the interdigital vein is an appropriate location to use when establishing a hematologic and biochemical profile for leatherback sea turtles.

Molecular characterization of factor V leiden G1691A and prothrombin G20210A mutations in Saudi newborns with stroke.

This study examined a possible association between the mutations related to Factor V Leiden and Factor II (prothrombin) and stroke in Saudi neonates. A multiplex PCR was established to detect Factor V Leiden G1691A and prothrombin G20210A mutations in 72 neonatal stroke subjects and 70 healthy adult controls with no family history of thromboembolic diseases. The frequency of the homozygous normal genotype (GG) of both genes was found to be significantly lower in the stroke subjects than in the controls (P < 0.0001). The stroke cases also had higher frequencies of the combined Factor II heterozygous mutant form (GA) and the homozygous normal Factor V (GG) (P < 0.0001) and of the combined heterozygous Factor V and the homozygous normal Factor II genotypes (GG) (P = 0.0) than controls. The study concluded that prothrombin and Factor V Leiden may be important risk factors for neonatal stroke in Saudi children.

Less common hemorrhagic coagulopathies in women.

Congenital coagulopathies are a group of hereditary conditions associated with significant hemorrhagic complications. Women with congenital coagulopathies tend to experience higher bleeding rates resulting from physiological processes and pregnancy and delivery. In these women, it is essential to recognize the symptoms and work in a coordinated way between hematologists and gynecologists.

Rapidly involuting congenital haemangioma associated with transient thrombocytopenia and coagulopathy: a case series.

Rapidly involuting congenital haemangioma (RICH) may present with thrombocytopenia, low fibrinogen and elevated fibrin degradation products and D-dimers. Such complications have rarely been reported. We wished to define the clinical characteristics of the thrombocytopenia and coagulopathy associated with RICH, to emphasize the transient nature of this haematological complication and to distinguish these abnormalities from true Kasabach-Merritt phenomenon (KMP). We present a case series of seven patients with large RICH who presented with thrombocytopenia and coagulopathy during the first week of life. Clinical and haematological characteristics were recorded retrospectively. Two of the patients were treated with embolization due to early signs of high-output cardiac failure; four patients received oral corticosteroids in the range of 2 mg kg(-1) daily; one patient did not receive any treatment in the neonatal period, although the tumour was excised at 6 months of age. Two patients with platelet counts lower than 10 x 10(9) L(-1) received a platelet transfusion. There were no bleeding complications and only one patient presented with petechiae. In all seven patients, platelet counts started to increase at > 2 weeks of age and the coagulopathy resolved. We conclude that RICH may present with thrombocytopenia and coagulopathy similar to mild KMP early in the neonatal period. However, in contrast to true KMP, these abnormal laboratory findings are self-limited and are usually not complicated by bleeding problems.

Familial deficiency of vitamin K-dependent clotting factors.

Combined deficiency of vitamin K-dependent clotting factors II, VII, IX and X (and proteins C, S, and Z) is usually an acquired clinical problem, often resulting from liver disease, malabsorption, or warfarin overdose. A rare inherited form of defective gamma-carboxylation resulting in early onset of bleeding was first described by McMillan and Roberts in 1966 and subsequently has been termed 'vitamin K-dependent clotting factor deficiency' (VKCFD). Biochemical and molecular studies identify two variants of this autosomal recessive disorder: VKCFD1, which is associated with point mutations in the gamma-glutamylcarboxylase gene (GGCX), and VKCFD2, which results from point mutations in the vitamin K epoxide reductase gene (VKOR). Bleeding ranges in severity from mild to severe. Therapy includes high oral doses of vitamin K for prophylaxis, usually resulting in partial correction of factor deficiency, and episodic use of plasma infusions or prothrombin complex concentrate. Recent molecular studies have the potential to further our understanding of vitamin K metabolism, gamma-carboxylation, and the functional role this post-translational modification has for other proteins. The results may also provide potential targets for molecular therapeutics and pharmacogenetics.

Diagnostic Single Gene Analyses Beyond Sanger.

Molecular testing of congenital coagulation and platelet disorders offers confirmation of clinical diagnoses, supports genetic counselling, and enables predictive and prenatal diagnosis. In some cases, genotype-phenotype correlations are important for predicting the clinical course of the disease and adaptation of individualized therapy. Until recently, genotyping has been mainly performed by Sanger sequencing. While next generation sequencing (NGS) enables the parallel analysis of multiple genes, the cost-value ratio of custom-made panels can be unfavorable for analyses of specific small genes. The aim of this study was to transfer genotyping of small genes involved in congenital coagulation and platelet disorders from Sanger sequencing to an NGS-based method. A LR-PCR approach for target enrichment of the entire genomic regions of the genes F7, F10, F11, F12, GATA1, MYH9, TUBB1 and WAS was combined with high-throughput sequencing on a MiSeq platform. NGS detected all variants that had previously been identified by Sanger sequencing. Our results demonstrate that this approach is an accurate and flexible tool for molecular genetic diagnostics of single small genes.

Chromatographic, ultracentrifugal, and related studies of fibrinogen "Baltimore".

Chromatographic, ultracentrifugal, and related studies of the fibrinogen of a patient with a congenital disorder of fibrinogen (fibrinogen "Baltimore" have provided evidence of structural differences from normal.Diethylaminoethyl-cellulose (DEAE-cellulose) gradient elution chromatography demonstrated two major peaks in the elution pattern of fibrinogen Baltimore as was the case for normal fibrinogen. However, the first peak of fibrinogen Baltimore was somewhat broader and more symmetrical and was eluted significantly later in the chromatogram than the corresponding peak of normal fibrinogen. Additionally, in some elution patterns, a shoulder on the ascending limb of peak 1 was present, suggesting the presence of chromatographically "normal" fibrinogen. Thrombin time determinations of eluted column fractions from a chromatogram of propositus fibrinogen supported this conclusion by demonstrating that fibrinogen from the ascending portion of peak 1 behaved functionally more like normal than that later in the chromatogram. Chromatograms of mixtures of propositus and normal fibrinogen confirmed the ability of this technique to distinguish normal from Baltimore fibrinogen. Chromatograms of fibrinogen isolated from two affected daughters displayed the characteristic increased anionic binding of peak 1 fibrinogen. Sedimentation velocity experiments indicated that the S(o) (20, [unk]) of fibrinogen Baltimore was slightly greater (8.13S vs. 7.85S) than that of normal fraction I-4. Differences in concentration dependence (- 0.65 c vs. - 1.30 c for normal) of the sedimentation coefficient could be attributable in part to spatial conformational differences. Molecular sieving experiments in acrylamide gels indicated that the molecular weight of propositus fraction I-2 was about the same as that of normal fibrinogen of comparable solubility (i.e. I-4, mol wt 325,000). Studies of the UV spectra, tyrosine/tryptophan ratios, sialic acid and hexose content, and N-terminal amino acids demonstrated no consistent significant differences from normal fraction I-4.

Factor XIII in human plasma and platelets.

Plasma and platelet factor XIII levels were measured in normal human donors and in a patient congenitally deficient in factor XIII. The purpose of these experiments was to study the role of platelet factor XIII in blood coagulation. On polyacrylamide disc electrophoresis, factor XIII activity in extracts of washed normal platelets appeared as a single peak. This peak was missing or very low when factor XIII-deficient platelet extract was used. The patient was also studied before and after transfusion of fresh frozen plasma. Before transfusion, factor XIII activity could not be detected in the patient's plasma or platelet extracts. 24 hr after transfusion the plasma factor XIII level was still at the anticipated value, but factor XIII activity could not be detected in the platelet extracts. These experiments imply that plasma factor XIII was not transported across the platelet membrane in measurable quantities in vivo. This suggests that platelet factor XIII is a true platelet component and originates in the platelet precursor, the megakaryocyte. Thrombelastographic studies suggest that platelet factor XIII participates in the coagulation process. Thrombelastograms of factor XIII-deficient samples had decreased maximum amplitude and clot elasticity values. The abnormalities were fully corrected by the addition of washed normal platelets to factor XIII-deficient plasma; preincubation of the normal platelets in the deficient plasma had no additional effect. This indicates that platelet factor XIII is immediately available during clot formation.

Congenital dysfibrinogenemia: fibrinogen Detroit.

A 17 yr old female with a congenital bleeding disorder was found to suffer from dysfibrinogenemia. Whole blood and plasma coagulation times were delayed and thrombelastograms were grossly abnormal. Clottability of plasma fibrinogen by addition of thrombin was not demonstrated during the 30 min test period. Fibrinogen was revealed by turbidometric and immunologic techniques. Other coagulation factors were present in normal amounts and prothrombin activation was normal. Patient's plasma inhibited thrombin clotting times of normal plasma and purified normal fibrinogen. Fibrinolysis was not detected. The plasma fibrinogen migrated normally on paper and cellulose acetate electrophoresis, but on immunoelectrophoresis it displayed a faster mobility than normal fibrinogen. On immunodiffusion the antigenic determinants were similar to those of normal fibrinogen. The patient's fibrinogen-antifibrinogen precipitins required longer to appear and the resultant precipitin was broader and hazier than those elicited with normal fibrinogen. These findings suggest the presence of two discrete populations of fibrinogen molecules. Investigation of the family of the patient suggested that the defect has an autosomal dominant pattern of heredity. Immunologic comparisons of our patient's plasma and of her relatives with plasma of patients with "Fibrinogen Baltimore" and "Fibrinogen Cleveland" revealed certain differences in immunoelectrophoretic mobility as well as in immunodiffusion. In keeping with the nomenclatures of abnormal fibrinogens in the literature, we propose the term "Fibrinogen Detroit" for this fibrinogen.Physicochemical properties of "Fibrinogen Detroit" were investigated also and compared with those of normal fibrinogen. Purified normal fibrinogen (clottability 96.7%) and "Fibrinogen Detroit" revealed homogeneity when studied by ultracentrifugation and immunoelectrophoresis. Native and cleaved "Fibrinogen Detroit" had the same sedimentation constants and molecular weights as the normal. In fresh samples. 3 moles of free SH groups/mole of fibrinogen were titrated in both. Determination of the amino acid composition revealed a decreased content of lysine, glucosamine, and galactosamine in abnormal fibrinogen. Total carbohydrates, protein-bound hexoses, sialic acid, and hexosamine were decreased in the abnormal fibrinogen. In an investigation with Doctors Blombäck a specific molecular defect was revealed in the N-terminal disulfide knot of the alpha (A) chain in which the arginine at the 19th position was replaced by serine. It is believed that the substitution of a strongly basic amino acid with a neutral hydroxy acid may result in considerable conformational changes in the N-terminal disulfide knot of fibrinogen which might affect the "active site" for polymerization. The lower carbohydrate content observed in "Fibrinogen Detroit" may have been the result of a change in primary and tertiary structure of the protein.

A molecular defect in thrombasthenic platelets.

An IgG antibody found in the serum of a thrombasthenic patient reacted in complement fixation with platelets from 350 normal individuals but was nonreactive with platelets from eight other thrombasthenic patients. ADP-induced aggregation of normal platelets was inhibited by the patient's antibody. Family studies using the quantitative complement fixation test showed that healthy heterozygotes were easily distinguishable from normal or thrombasthenic individuals since their platelets had an intermediate amount of the reactive antigen. Indirect immunoprecipitation tests using this serum and soluble membrane antigens labeled with iodine-125 that had been extracted from normal platelets by the detergent Nonidet P-40 gave a single radioactive peak at 120,000 mol wt in sodium dodecyl sulfate polyacrylamide gel electrophoresis. A similar estimate of the molecular weight was obtained from Sephadex G-200 filtration of the soluble antigens extracted from normal platelets by spontaneous release or chaotropic agents and tested in complement fixation with the patient's serum. These findings strongly suggest that the molecule recognized by this antibody is absent or structurally modified in thrombasthenia cases and that it may be involved in platelet aggregation.