Search PubMed⌕ Search

Biomedical subjects

A L Bloom

Publications and source records attributed to A L Bloom.

At least 73 records · Page 4Linked to original sources
PubMed1981

Carrier detection in haemophilia a by immunological measurement of factor VIII related antigen (VIIIRAg) and factor VIII clotting antigen (VIIICAg).

23 obligate carriers of mild and severe haemophilia A and 26 normal females were bled on three occasions, and their plasmas assayed for procoagulant factor VIII (VIIIC), factor VIII related antigen (VIIIRAg) and factor VIII clotting antigen (VIIICAg). A comparison of the ratios VIIIC/VIIIRAg and VIIICAg/VIIIRAg indicated that, although the two ratios gave the same proportional misclassification of carriers as normals (four of 23), the latter ratio showed greater discriminatory power when an unequal variances predictive method was used to calculate likelihood ratios (for carrier status). This greater power was shown to be due to a greater reproducibility between visits for the VIIICAg/VIIIRAg ratio. Discrimination was considerably better when the median of the three median values for each variable was analysed, compared to the median value obtained at the first visit. There was also no statistical difference between VIIICAg/VIIIRAg (or VIIIC/VIIIRAg) ratios obtained from carriers of severe compared to mild haemophilia.

Antigens↗
PubMed1981

Tentative protocol for the evaluation of coagulometers, based on one-stage prothrombin time.

Information on performance is invaluable to those who have to decide on the choice of an instrument. More interest is being shown in the use of coagulometers. Accordingly, a tentative protocol for the evaluation of coagulometers is presented for discussion. While it is based on the use of one-stage prothrombin time, principles of evaluation are laid down which should make it generally applicable. It is hoped that the tentative protocol will form the basis of a reference protocol and to this end comments are invited from users of coagulometers and suppliers. Comments for publication may be sent to the Editor of Clinical and Laboratory Haematology or to the Secretary of the Working Party.

Blood Coagulation Tests↗
PubMed1980

Dual diagnosis of prenatal haemophilia A by measurement of fetal factor VIIIC and VIIIC antigen (VIIICAg).

Procoagulant factor VIII (VIIIC) and procoagulant factor VIII antigen (VIIICAg) were measured in 20 samples of pure fetal blood obtained by fetoscopy at mid-term from non-haemophilic fetuses. VIIIC levels ranged from 25 to 89 U/dl (mean 43.5) and VIIICAg from 11 to 43 U/dl (mean 22.3). Samples from 39 consecutive fetuses at risk of haemophilia A gave results indicating haemophilia in 11, and these pregnancies were terminated at the parents' request. Of the remaining 28, 18 have resulted in normal births, 8 still await delivery, and 2 pregnancies were terminated for non-haematological reasons. The results confirm that pure fetal blood can be aspirated fetoscopically for plasma assays of both VIIIC and VIIICAg. Dual measurement enhances the reliability of predicting or excluding haemophilia A, and makes prenatal diagnosis a dependable option for known or potential carriers seeking this information.

Antigens↗
PubMed1980

Familial haemostatic defect associated with reduced prothrombin consumption.

Ten individuals from three unrelated families suffered from an usual inherited haemorrhagic disorder. The defect was associated with reduced prothrombin conversion as shown by a grossly abnormal prothrombin consumption index. All known plasma coagulation factors were present in adequate concentrations but in the two families tested the results were consistent with a defect of the interaction between plasma and platelets or phospholipid. Some of the affected family members exhibited a mild bleeding tendency characterized by post-operative or post-partum haemorrhage but none suffered spontaneous bleeding. In therapeutic trials in one of the patients both plasma and platelet transfusions were needed in order to correct the abnormality. This finding together with in vitro and other in vivo studies indicated that the abnormality is associated with an inhibitor of the interaction between plasma and phospholipid during blood coagulation. The results suggest the possibility of an abnormality of the gamma-carboxyglutamic acid residues of one or more vitamin K dependent coagulation factors but immunological and electrophoretic studies have so far failed to detect this. The findings underline the importance of a test of prothrombin conversion in screening procedures for an otherwise unexplained bleeding disorder.

Adolescent↗
PubMed1980

Factor VII and fibrinolytic response to deamino-8-D-argenine vasopressin in normal subjects and dissociate response in some patients with haemophilia and von Willebrand's disease.

Deamino-8-D-argenine vasopressin (DDAVP) was given by intravenous infusion to normal subjects, haemophiliacs and patients with von Willebrand's disease (vWd) and the factor VIII and plasminogen activator response was studied. In normal subjects and most patients with mild haemophilia and mild (intermediate) von Willebrand's disease there was an increase in plasminogen activator and all factor VIII related activities. In patients with mild vWd the prolonged bleeding time was shortened by DDAVP despite only a modest rise in factor VIII related Ristocetin cofactor activity (VIIIR:RiCoF). Sub-groups of patients have been characterized in whom atypical responses was observed. In two brothers with clinically severe haemophilia, but with 5--6 u/dl procoagulant factor VIII (VIIIC), there was an increase in VIIIC but no rise of the corresponding antigen, suggesting increased release of an antigenically abnormal poorly functioning molecule. A patient with intermediate vWd was studied in whom neither DDAVP, adrenaline infusion, nor venous occlusion resulted in an increase in either plasminogen activator or factor VIII related antigen (VIIRAg), although there was a significant increase in VIIIC. In a further patient with severe vWd, DDAVP failed to elicit any plasminogen activator or VIII response. The results obtained from these two patients suggested that in some individuals the presumed endothelial cell abnormality in vWd may be more extensive than a defect in VIIIRAg synthesis. Sub-groups of patients have been identified for whom treatment with factor VIII concentrates would be more appropriate than DDAVP prior to minor surgery.

Adolescent↗
PubMed1980

Characterization of procoagulant activity produced by cultures of human monocytes and lymphocytes separated in colloidal silica-polvinylpyrrolidone gradients.

Human peripheral blood leucocytes were examined for their ability to synthesize procoagulant activity in tissue culture. A method was developed utilizing silica coated with polyvinylpyrrolidone (Percoll) to separate monocytes from lymphocytes prior to culture. Coagulation activity was demonstrated in all mononuclear cell cultures after 24 hours incubation. This activity was inhibited by phospholipase C which suggested that tissue thromboplastin was the major source of activity. Specific immunoradiometric assays failed to demonstrate synthesis of factor VIII related antigen (FVIIIRAG) or factor VIII coagulant antigen. The results indicate that under conditions of this study factor VIII was not synthesized in mononuclear cell cultures.

Cell Separation↗
PubMed1979

Factor VIII: new clinical and genetic aspects.

Factor VIII is a complex molecule comprising a series of homologous oligomers with biological activity related to primary haemostasis (factor VIII related antigen/Willebrand factor; FVIIIRAg/WF). The structure or distribution of these oligomers is abnormal in von Willebrand's disease (vWd). The oligomers are associated with, or contain, a lower molecular weight entity with procoagulant activity (factor VIIIC) which has distinct antigenic determinants and is reduced or abnormal in haemophilia. Recessive and dominant forms of vWd have been recognised but two families are described each with features of both dominant and recessive inheritance; this is of importance in genetic counselling. Results of a new immunoradiometric assay for factor VIIIC antigen showed reduced levels in vWd and haemophilia and it was absent in 3 of 6 samples from fetuses of obligate carriers of haemophilia. The potential use of this assay for the prenatal diagnosis of haemophilia is described.

Epitopes↗
PubMed1979

Factor VIII inhibitor and bronchogenic carcinoma.

An inhibitor to procoagulant factor VIII (FVIIIC) developed in a patient three years after palliative resection of a bronchogenic carcinoma. The inhibitor was not active against ristocetin cofactor but possibly had some activity against factor XI. It responded to immunosuppressive therapy. This is apparently the first reported association of carcinoma and factor VIII inhibitor.

Blood Coagulation Tests↗
PubMed1979

An immunoradiometric assay for procoagulant factor VIII antigen: results in haemophilia, von Willebrand's disease and fetal plasma and serum.

An immunoradiometric assay (IRMA) has been developed based on the inhibitor which arose in a polytransfused severe haemophiliac. The two-site IRMA measures antigens closely associated with the procoagulant parts of the factor VIII complex, which are termed FVIIC antigens or FVIIICAG. FVIIICAG was present in normal plasma and also, at a slightly lower concentration, in normal serum. In 37 patients with haemophilia A, 36 had FVIIICAG levels of less than 10% of the normal plasma pool. In patients with von Willebrand's disease the levels of FVIIIC and FVIIICAG were in good agreement, both before and after treatment with cryoprecipitate or DDAVP. FVIIICAG was relatively stable in plasma at 37 degrees C and could also be detected in cord and fetal serum. The assay is of potential value for detecting reduced levels of factor VIII, for carrier detection and for the prenatal diagnosis of haemophilia.

Antigens↗