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S J Machin

Publications and source records attributed to S J Machin.

At least 91 records · Page 5Linked to original sources
PubMed1995

The use of an anti-beta 2-glycoprotein-I assay for discrimination between anticardiolipin antibodies associated with infection and increased risk of thrombosis.

Antiphospholipid antibodies (aPAs), occurring in association with infection, are not generally associated with an increased risk of thrombosis. Anticardiolipin antibodies (aCL) from patients with infection, unlike those from patients with SLE, do not have the beta 2GPI cofactor requirements. Antibodies to beta 2GPI (alpha beta 2GPI) are more closely associated with a previous history of thrombosis than aCL in patients with SLE. In the present study we have investigated the reactivity of the alpha beta 2GPI assay for aPAs associated with infection. Serum from 114 patients with infections including syphilis (n = 11), tuberculosis (n = 63) and Klebsiella (n = 42) were assayed for alpha beta 2GPI and aCL antibodies. The incidence of aCL in serum of patients with tuberculosis. Klebsiella infection and syphilis was 6.0%, 5.0% and 64.0%, respectively, but all patients were negative for alpha beta 2GPI. These results indicate that the alpha beta 2GPI assay is negative in patients with transiently positive aCL assays associated with infection.

Adult↗
PubMed1995

Two-centre evaluation of the Abbott CD3500 blood counter.

The CD3500 blood counter (Abbott Laboratories) is a 33 parameter fully automated blood counter that produces a five part differential count with flagging of leucocyte abnormalities. In this evaluation excellent correlation between CD3500 and Coulter STKR blood counter was found for all red cell and platelet parameters on the 221 samples tested. Studies of carryover, mixing efficiency and precision also gave excellent results. There was a good correlation with manual 400 cell differential counts for neutrophils, lymphocytes, monocytes and eosinophils for the 468 samples compared. Correlation of CD3500 and manual basophil counts was poor. Normal samples stored at 4 degrees C and analysed while cold showed satisfactory stability for WBC, RBC, Hb, MCV and platelets for 48 h and a stable differential for 24 h. Correlation with the differential count produced by the Coulter STKS showed good correlation for neutrophils, lymphocytes, monocytes and eosinophils; correlation with STKS basophils was poor. False positive flagging rate varied between 8.9% (Band and/or IG) and 0.9% (NRBC) depending on the nature of the flag; 5.8% of samples exhibited two or more false positive flags. No significant breakdowns were encountered during the period of the evaluation. The scatterplot displays of laser light scatter produced by the instrument provide an interesting adjunct to conventional morphology.

Blood Cell Count↗
PubMed1995

Balancing the risk of recurrent thromboembolism and pre-existing osteoporosis in pregnancy.

In summary, our 31-year-old patient with hypogonadotrophic hypogonadism has severe osteoporosis caused by chronic oestrogen deficiency. Her GnRH deficiency can be overcome using ovulation induction therapy. However, if she becomes pregnant there is a small risk of recurrent thromboembolism because of her previous cerebral thrombosis. This risk is hard to quantify but would undoubtedly increase if her mobility were impaired. The metabolic and mechanical alterations of pregnancy may compromise her weakened skeleton and increase the risk of a second major fracture. Her skeletal status precludes the use of standard heparin. Fractionated low molecular weight heparins would be the prophylactic agent of choice, possibly switching to low-dose warfarin for the second trimester. Alternative prophylaxis using low-dose aspirin may be suitable, although this is not proven. The difficulty in this case is that pregnancy and the prophylactic measures designed to protect the patient may prove to be detrimental. The case also highlights the vital role of prepregnancy counselling and interdisciplinary consultation between obstetrician, haematologist and endocrinologist in order to steer the safest course through this therapeutic minefield.

Adolescent↗
PubMed1995

Evaluation of a semi-automated reticulocyte counting method using the Coulter STKS-2A blood cell counter.

Reticulocyte counting was assessed on the Coulter STKS-2A automated blood cell counter. Using a two step procedure, blood samples were first incubated with the supravital stain new methylene blue. An acidic reagent was then added to clear the haemoglobin and any stained RNA was preserved within the cell. The cells were then analysed by measurement of volume, conductivity and light scatter (VCS). The results of 123 samples analysed on the STKS-2A were compared with those from a Toa Sysmex R-1000 reticulocyte counter. One hundred and seven samples gave no review flags and reticulocyte counts ranging from 0.5% to 22.8%, resulting in a correlation coefficient of 0.93 for the methods. Between run imprecision studies gave CVs ranging from 5.3% for a reticulocyte count of 8.7% to a CV of 16.3% for a 0.34% count. Stability studies showed insignificant changes over 72 h storage. These findings confirm that VCS technology can be adapted to provide precise and accurate routine reticulocyte analysis.

Automation↗
PubMed1995

Platelet transfusion.

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Antigens, Human Platelet↗
PubMed1994

Beta 2 glycoprotein-I antigen is increased in primary hyperlipidaemia.

In order to determine whether elevated levels of beta 2 glycoprotein-I (beta 2GPI) are associated with increased plasma lipids, we measured plasma beta 2GPI antigen levels in 47 patients with primary hyperlipidaemia (20 severe hypercholesterolaemia, nine severe hypertriglyceridaemia, and 18 mixed hyperlipidaemia) and 34 normal healthy subjects. Mean beta 2GPI levels were significantly increased in each patient group (302.3, 272.9 and 299.1 mg/l, respectively) compared to controls (199.6 mg/l) (P < 0.01). Significant correlations were demonstrated between beta 2GPI levels and triglyceride and total cholesterol levels in the control group (r = 0.387, r = 0.559; P < 0.05), but were not observed in all patient groups. These results indicate that beta 2GPI is increased in hyperlipidaemia and that its distribution between plasma lipid fractions is perturbed. Plasma lipid levels should therefore be considered when interpreting results of beta 2GPI antigen assays.

Adult↗
PubMed1994

A new type of pseudothrombocytopenia: EDTA-mediated agglutination of platelets bearing Fab fragments of a chimaeric antibody.

In vitro agglutination of platelets leading to low automated platelet counts was observed in EDTA-anticoagulated blood from human volunteers receiving infusions of Fab fragments of a chimaeric monoclonal antibody to platelet glycoprotein IIb-IIIa. This pseudothrombocytopenia depended on the presence of chimaeric Fab on the platelet surface and was not seen when sodium citrate was used as anticoagulent. Preliminary evidence suggests that this phenomenon might be mediated by immunoglobulin G reactive with the human component of the chimaeric Fab. It is important to exclude pseudothrombocytopenia when low automated platelet counts are reported in association with the administration of chimaeric anti-platelet antibodies.

Blood Platelets↗
PubMed1994

Acquired pseudo-pseudo Bernard-Soulier syndrome complicating Gaucher's disease.

AIMS: To investigate the abnormality in platelet function in two patients with type I Gaucher's disease causing a chronic bleeding tendency despite normalisation of the platelet count after spleen removal. METHODS: Routine laboratory methods were used to assess baseline coagulation. Platelet aggregometry was used to assess platelet responses to a range of agonists, and abnormalities were further assessed in mixing experiments using washed platelets and patients' plasma. RESULTS: Platelets from both patients with Gaucher's disease failed to agglutinate to ristocetin, despite normal platelet surface glycoprotein (GP) Ib and plasma von Willebrand factor activity. The agglutination of normal washed platelets was abolished by incubation in patient plasma. The inhibitory activity did not lie in the IgG fraction of patient plasma, and was found to be loosely associated with the patient platelet surface. CONCLUSIONS: The inhibition of ristocetin induced platelet agglutination in patients with Gaucher's disease causes a prolonged skin bleeding time. This could be due to the accumulated glucocerebroside in the plasma coating the platelet membrane. It is suggested that the term pseudo-pseudo Bernard-Soulier syndrome would be appropriate, as on initial screening, the abnormality has the features of Bernard-Soulier syndrome, but further investigation shows normal plasma von Willebrand activity and platelet surface GP Ib concentrations. The inhibitory activity is not due to a platelet specific antibody as is the case in pseudo-Bernard Soulier syndrome.

Adult↗
PubMed1994

The Taipan snake venom time: a new test for lupus anticoagulant.

AIMS: To develop a specific test for lupus anticoagulant activity with reduced sensitivity to coagulation factor deficiency that would be suitable for analysis of plasmas from patients receiving oral anticoagulants. METHODS: A coagulation test based on the Taipan snake venom time (TSVT) with a platelet neutralisation procedure (PNP) was developed and compared with dilute Russell's viper venom time (DRVVT). The TSVT was used to test plasmas from patients receiving oral anticoagulant or heparin with mild liver dysfunction and with documented lupus anticoagulant. RESULTS: The optimised conditions for the TSVT were established and a reference range was determined in normal healthy subjects. Results were considered positive for lupus anticoagulant if the ratio was > or = 1.1 and was reduced by > or = 10% or to < 1.1 in the PNP. In 43 samples from patients receiving oral anticoagulants there was no correlation between level of anticoagulation and TSVT, and only seven samples had increased TSVTs. Of these, five corrected on mixing with normal plasma and two gave equivocal results. The patients with mild liver dysfunction all had normal TSVTs. The TSVT in plasmas from patients receiving heparin correlated with the heparin concentrations (as measured by the APTT, r2 = 0.81). Some anticoagulated plasmas showed correction in the PNP and were regarded as false positive. Fourteen of 17 patients known to have lupus anticoagulant (on the basis of DRVVT results) were also positive by the TSVT; two of the remaining three were borderline and one was negative. CONCLUSIONS: The TSVT showed satisfactory intra-assay precision and reasonable sensitivity to lupus anticoagulant, compared with the DRVVT. The TSVT was influenced by the presence of heparin but was not sensitive to the effects of oral anticoagulant. Like other lupus anticoagulant tests, it does not seem to have a 100% detection rate, but this may be due to the presence of lupus anticoagulant subtypes with distinct activities or the requirement of cofactors other than prothrombin or beta 2 glycoprotein-I.

Adult↗
PubMed1994

The interaction of beta 2 glycoprotein-I and heparin and its effect on beta 2 glycoprotein-I antiphospholipid antibody cofactor function in plasma.

beta 2 glycoprotein-I (beta 2GPI), a cofactor for antiphospholipid antibody (aPA) binding, binds to many anionic macromolecules including heparin. The nature of this interaction with heparin is not well understood and its effect on the purported biological functions of beta 2GPI is unknown. We have examined the interactions of dermatan sulphate (DS) and different pharmaceutical preparations of heparin with beta 2GPI by crossed immunoelectrophoresis (CIE) and investigated the effect of these agents on plasma levels of beta 2GPI antigen (beta 2GPI:Ag) by a standardised enzyme linked immunosorbent assay (ELISA). beta 2GPI aPA cofactor activity (beta 2GPI:Cof) was also measured using a modified solid phase anti-phosphatidylserine (aPS) ELISA. CIE results confirmed a heparin-beta 2GPI interaction with unfractionated (UF) heparin. beta 2GPI:Ag levels were unaffected by any of the preparations investigated. There were no significant differences in beta 2GPI:Cof activities of the samples containing LMW heparins or DS but levels of beta 2GPI:Cof were increased in samples containing UF sodium and calcium heparin preparations (0.5 IU/ml Monoparin, p < 0.05, and 10 IU/ml Liquemin and Calciparine, p < 0.05).

Antibodies, Antiphospholipid↗
PubMed1993

Immunoelectrophoresis and ELISA techniques for assay of plasma beta 2 glycoprotein-1 and the influence of plasma lipids.

Beta 2 glycoprotein-1 (beta 2GP1) has been identified as a cofactor for the binding of some antiphospholipid antibodies to anionic phospholipids and has been demonstrated to possess anticoagulant properties in vitro. We have investigated Laurell rocket immunoelectrophoresis (IEP) and ELISA techniques for measurement of beta 2GP1. Western blotting and crossed immunoelectrophoresis (CIE) of plasma demonstrated free beta 2GP1 and beta 2GP1 complexed with unidentified plasma constituents. The free and complexed forms were not distinguished in immunoelectrophoresis assays, allowing measurement of total beta 2GP1. Standard and detergent modified IEP and ELISA techniques were compared: significant correlation was demonstrated between unmodified and detergent modified IEP, detergent modified IEP and ELISA and unmodified IEP and ELISA. The intra-assay co-efficients of variation (CVs) of the unmodified and modified IEPs and ELISA were 7.5, 3.7 and 7.9%. Inter-assay CVs determined for the modified IEP and ELISA were 5.8 and 9.1% respectively. The purified beta 2GP1 used to standardise the assays was shown to have subfraction selectivity and different calibration values were obtained for pooled normal plasma by the unmodified IEP (242 mg/l) and modified IEP and ELISA (201 mg/l). We have also investigated the influence of some pre-test variables on beta 2GP1 levels and shown that heparin, citrate or EDTA plasma and serum samples are suitable for assay of this glycoprotein and that levels are unaffected by repeated freeze/thawing. The influence of plasma lipids on beta 2GP1 measurement was also examined and we demonstrated no significant differences between pre and postprandial samples, which suggests that fasting status is not an important consideration for assay of beta 2GP1 in healthy subjects.

Apolipoproteins↗
PubMed1993

Postoperative multiple organ dysfunction syndrome associated with gut mucosal hypoperfusion, increased neutrophil degranulation and C1-esterase inhibitor depletion.

We have examined the relationship between gut mucosal perfusion, as determined by gastric intramucosal pH (pHi), changes in plasma neutrophil elastase concentrations and components of the contact system during elective major surgery and related these findings to patient outcome. Of the 26 patients studied, 16 developed gut mucosal hypoperfusion (pHi < 7.32) by the end of surgery; four of these developed multiple organ dysfunction syndrome; three of these died. In this group there was a significant increase in neutrophil elastase (P < 0.005) and significant reductions in plasma components of the contact system from immediately before surgery to 24 h later. Ten patients maintained gut mucosal perfusion (pHi > or = 7.32); none of these developed life threatening complications. In this group there was no significant increase in neutrophil elastase and, although there were significant reductions in some plasma components of the contact system, concentrations of C1-esterase inhibitor (the main inhibitor of the contact system) were not significantly reduced. We conclude that gut mucosal hypoperfusion, neutrophil degranulation and activation of the contact system to the extent that C1-esterase inhibitor becomes depleted are associated with a poor outcome after major surgery.

Adult↗
PubMed1993

Sickle cell disorders and chronic intravascular haemolysis are associated with low plasma heparin cofactor II.

Thrombotic events are known to be increased in patients with sickle cell syndromes and a variety of abnormalities of coagulation or endothelial function have been described, although the relevance of these findings either to the pathogenesis of vaso-occlusive phenomena or the risk of thrombosis are unclear. Heparin cofactor II (HCII) and antithrombin III are circulating inhibitors of thrombin and low plasma levels have been associated with an increased risk of thrombosis in otherwise healthy individuals. We describe for the first time abnormally low plasma levels of HCII in patients with sickle cell syndromes. 45 adult patients with sickle cell syndromes (31 SS, 10 SC, 4 S beta Thal) were compared with 61 age matched control patients for HCII in plasma. There was a highly significant reduction in HCII in SS patients irrespective of crisis or transfusion state 0.68 +/- 0.15 U/ml (mean +/- SD) compared with controls 1.00 +/- 0.19 U/ml (P < 0.001). HCII antigen was also significantly reduced (0.53 +/- 0.19 U/ml) compared with controls (1.02 +/- 0.23 U/ml, P < 0.0001). By contrast there was no reduction in antithrombin III in this group. HCII (0.63 +/- 0.13 U/ml, P < 0.001) and HCII antigen (0.54 +/- 0.08 U/ml, P < 0.001) are also significantly reduced in SC patients HCII levels increased towards control values during sickle cell crises, in patients taking the contraceptive pill, or with regular blood transfusion; however, plasma HCII concentrations were not increased acutely by exchange transfusion. HCII was also decreased in thalassaemia intermedia and pyruvate kinase deficiency, suggesting that intravascular haemolysis may be the cause of reduced HCII levels.

Adult↗
PubMed1993

Life-threatening thrombotic and haemorrhagic problems associated with silent myeloproliferative disorders.

Myeloproliferative disorders are well recognized as being associated with haemorrhage and thrombosis. We describe two cases, one of life-threatening haemorrhage and the other of thrombosis, in patients with normal peripheral blood counts and films, both of whom went on to develop overt manifestations of myeloproliferative disorders (CGL and essential thrombocythaemia) more than a year after their first presentation.

Adult↗
PubMed1993

A flow-cytometric approach to quantitative estimation of platelet surface immunoglobulin G.

Flow cytometry (FC) was used to estimate platelet-surface IgG (PSIgG) by quantifying the fluorescence of platelets incubated with a fluorescein isothiocyanate (FITC)-labelled polyclonal goat anti-human IgG antibody or FITC-labelled non-immune goat IgG. Results were expressed as relative fluorescence intensity (RFI) defined as the ratio of specific fluorescence (mean fluorescence of platelets incubated with the FITC anti-IgG) over non-specific fluorescence (mean fluorescence of platelets incubated with FITC non-immune goat IgG). A normal range was formed by analysing platelets from 71 healthy subjects. Platelets from 16 patients with a firm clinical diagnosis of immune-mediated thrombocytopenia had a mean RFI significantly higher (p < 0.001) than the controls, whereas platelets from 9 patients thought to have non-immune thrombocytopenia had an RFI not significantly different from the normal controls. From a prospectively studied group of 62 patients with no clinically obvious cause for their thrombocytopenia or impaired platelet function 35.5% had raised PSIgG. In order to express the results as number of IgG molecules per platelet, reference curves were created by using FC to measure PSIgG of platelets coated with known amounts of a chimeric IgG (human IgG with murine hypervariable region) monoclonal antibody to the glycoprotein IIb-IIIa complex. Normal platelets had an average 1,463 (SD = 927) molecules of PSIgG. In patients with immune-mediated thrombocytopenia the levels ranged from 690 to 32,328 (mean 11,535) molecules per platelet. Flow-cytometric PSIgG estimation was sensitive, fast and easy to perform and therefore suitable for both research and clinical service purposes.

Adult↗
PubMed1993

Contact factor mediated fibrinolysis is increased by the combined oral contraceptive pill.

OBJECTIVE: To study the fibrinolytic pathways and their relationship with the contact system in women using combined oral contraceptives (COCs). DESIGN: Serial plasma samples were collected from 18 women before treatment with COCs containing 30 micrograms oestrogen during treatment cycles 3 and 6, and 2 weeks after stopping treatment. Fibrinolysis was measured before and after dextran sulphate mediated contact activation using fibrin plates. RESULTS: Fibrinolysis increased significantly during cycles 3 and 6 (from 77% to 100% and 113%, respectively, P < 0.01) and showed a further increase after dextran sulphate activation (from 134% to 158% and 167%, respectively, P < 0.01). Tissue-plasminogen activator, urokinase-plasminogen activator and plasminogen activator inhibitor did not change significantly. There were significant elevations of Factor XII (from 0.92 u/ml to 1.43 u/ml, P < 0.01) and prekallikrein (0.94 u/ml to 1.10 u/ml, P < 0.05) in cycle 3, which both remained high at cycle 6 (P < 0.01) and decreased after stopping the COC. Alpha-2-macroglobulin and C1-esterase inhibitor showed no significant change, but alpha-1-antitrypsin increased from 0.85 u/ml to 1.11 u/ml by cycle 3 (P < 0.01), and returned to near normal levels after stopping the COC. CONCLUSIONS: The increase in fibrinolysis may be due to increased levels of Factor XII and prekallikrein without a corresponding increase in their natural inhibitors (C1-esterase inhibitor and alpha-2-macroglobulin). A parallel increase in the intrinsic pathway of coagulation may be limited by elevated alpha-1-antitrypsin at the level of activated Factor XI. The increase in fibrinolysis caused by oral contraceptives may balance any potential thrombotic risk due to increased fibrinogen or vitamin K dependent coagulation factors.

Adolescent↗
PubMed1993

A prospective randomized study of prophylactic teicoplanin to prevent early Hickman catheter-related sepsis in patients receiving intensive chemotherapy for haematological malignancies.

In all, 88 patients with haematological malignancies requiring Hickman catheters for intensive chemotherapy were randomized to receive either one single bolus intravenous injection of teicoplanin, 400 mg, or no teicoplanin immediately before insertion of a double-lumen Hickman catheter. Lower incidences of catheter-related Gram-positive sepsis were recorded in patients receiving prophylactic teicoplanin; exit site infection, tunnel infection and catheter-related Gram-positive septicaemia were all reduced. The benefit of prophylactic teicoplanin was observed particularly among patients who were already neutropenic at the time of catheterization. All Gram-positive organisms isolated from infected skin sites or from blood cultures taken from Hickman catheters were susceptible to teicoplanin. No adverse reaction was reported in any of the patients receiving prophylaxis. Prophylactic teicoplanin, therefore, may be used routinely for patients requiring insertion of Hickman catheters for intensive chemotherapy, to reduce the early incidence of catheter-related sepsis, particularly during the period of neutropenia following chemotherapy.

Adolescent↗