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Biomedical subjects

L Poller

Publications and source records attributed to L Poller.

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

An assessment of an amidolytic assay for factor VII in the laboratory control of oral anticoagulants.

A comparison has been made between the prothrombin time test using British Comparative Thromboplastin (BCT) and a chromogenic substrate assay for factor VII in the assessment of laboratory control of oral anticoagulants in short-term and long-term patients. Opportunity was also taken to compare the findings with parallel results obtained with the venous Thrombotest technique and a specific clotting assay for factor VII. There was good agreement between the amidolytic factor VII assay, using a method modified from Seligsohn et al (1978) with the Quick test using BCT and Thrombotest in 60 long-term patients. Tests in 53 patients within the first 3 weeks of starting oral anticoagulant administration gave less satisfactory agreement between the above amidolytic method and the conventional tests. In contrast, there was a good correlation between the two conventional tests in both groups and also between the clotting and amidolytic factor VII method. Although the results are an improvement on previous, less satisfactory correlations between the BCT prothrombin time method and amidolytic assays for factor II and X, the present study indicates the limitations of a specific clotting assay versus a broad spectrum extrinsic clotting test in oral anticoagulant control. While not warranting the routine use of the chromogenic assay for factor VII in place of the prothrombin time using BCT, the factor VII amidolytic assay offers a limited but dependable guide to dosage in long-term patients. The complexity of the technique in its present form militates against its adoption for routine anticoagulant control in hospital laboratories.

Acenocoumarol↗
PubMed1981

A study of the procoagulant properties of amniotic fluid and their correlation with the lecithin/sphingomyelin ratio.

The procoagulant properties of amniotic fluid have been studied in samples taken throughout pregnancy and the results correlated with the lecithin/sphingomyelin ratio: acceleration effects on the prothrombin time. Russell's viper venom test, activated partial thromboplastin time and specific factor VII and X assays and contact acceleration. Although amniotic fluid is shown to function as a complete thromboplastin and to activate factor X directly, none of these tests of procoagulant activity of amniotic fluid is a reliable index of fetal lung maturity.

Amniotic Fluid↗
PubMed1981

Prostacyclin-like, and kallikrein activity of amniotic fluid in pre-eclampsia.

Amniotic fluid from patients with pre-eclampsia was compared with samples obtained from normotensive controls with respect to the inhibiting effect on platelet aggregation (PGI2-like activity) and activating effect on the plasma kallikrein assay and Russell's viper venom test. After 39 weeks gestation, amniotic fluid from pre-eclamptic patients showed significantly less PGI2-like activity ( p less than 0.01) and significantly lower kallikrein levels (p less than 0.01) than that from normotensive controls. The study suggests that the biosynthesis and release of PGI2-like activity and kallikrein may be impaired in pre-eclampsia. In view of the association of pre-eclampsia with intravascular clotting, the highly significant reduction of PGI2-like activity seems important and appears to warrant a clinical trial of prostacyclin administration in this disorder.

Amniotic Fluid↗
PubMed1980

Heparin and partial thromboplastin time: an international survey.

The reliability of routine partial thromboplastin time (PTT) methods in the measurement of the anticoagulant effect of heparin has been assessed in a study involving over 300 hospitals in the U.S. and overseas. Commercial PTT methods were relatively insensitive to heparin, added in vitro, compared with the standardized PTT method tested by the same laboratories. Non-commercial, locally-prepared reagents compared well with the standardized method particularly in the detection of a low concentration of heparin. The value of a sensitive reference preparation for the calibration of routine PTT reagents used in heparin control is demonstrated.

Blood Coagulation↗
PubMed1980

The British Comparative Thromboplastin: the relationship between lipid class composition and procoagulant activity.

Twenty-eight consecutive batches of the reference reagent British Comparative Thromboplastin (BCT) were produced in the National (UK) Reference Laboratory for Anticoagulant Reagents and Control (NRLARC) between 1969 and 1977. The relationship between procoagulant activity and lipid class composition in these batches at various stages of age deterioration on storage has been studied by a modification of the method of high pressure chromatography which allows better definition of the individual lipids. The free fatty acid concentration rose markedly while cconcentrations of phosphatidyl choline, phosphatidyl ethanolamine and phosphatidyl serine were reduced. An oxidative process is suggested and supported by the increase in malonaldehyde levels. The method of production of the BCT involves maceration of human brain which causes the breakdown of cell membranes and the release of many potentially oxidative materials from subcellular particles. The loss of procoagulant activity of BCT on storage may be due to the loss of phospholipid or to the increase of inhibitory degradation products, i.e. free fatty acid and malonaldehyde. The examination of the lipid class composition of tissue thromboplastin extracts appears useful, therefore, not only in determining the phospholipids necessary for procoagulant activity, but also in monitoring the deterioration of tissue thromboplastins on storage.

Humans↗
PubMed1980

Fibrinogen determination in a series of proficiency studies.

Fibrinogen estimations were performed in four quality control proficiency studies conducted by the National (UK) Reference Laboratory for Anticoagulant Reagents and Control for over five hundred hospitals in the UK and overseas during 1976--1978, to evaluate the various techniques in current practice. More than 30 different estimation techniques were employed by participants and these could be classified into eight groups. The success in detecting a fibrinogen level below the normal range ('sensitivity') and reliability in providing a normal result for a value within the normal range ('specificity') have been determined. No method failed in both aspects. The tyrosine, clot weight, immunological and Clauss technique appeared reasonably satisfactory. The best results were obtained with the Clauss technique although the difference between this and the other quantitative techniques did not achieve statistical significance. Some were less dependable, notably the turbidity techniques and the thrombin time. Although no technique appeared to be superior to others from the standpoint of precision, turbidity techniques appeared to be the least precise showing the largest co-efficient of variation.

Fibrinogen↗
PubMed1980

A double-blind cross-over study of piperazine oestrone sulphate and placebo with coagulation studies.

A double-blind trial of piperazine oestrone sulphate was performed over a period of 14 months on 55 menopausal women complaining of depressiona and hot flushes. Depression was not affected but the hot flushes were significantly lessened by the oestrogen treatment. After three months of piperazine oestrone sulphate there were no significant accelerations of prothrombin time or increases in factors VII or X but, after six months, there was an acceleration in the prothrombin time. After 14 months those who received piperazine oestrone sulphate for the first six months showed a significant increase in alpha 1-antitrypsin and factor VIIR:AG. Oestrone piperazine sulphate appears to produce less marked changes in coagulation than oestrogen-containing oral contraceptives or conjugated equine oestrogens.

Blood Coagulation↗
PubMed1980

Standardization of the APTT test. Current status.

The partial thromboplastin time (PTT) which is used as an overall measure of the intrinsic clotting system, is the commonest coagulation test employed in routine laboratories apart from the prothrombin time. The main functions of the test are: - 1. to screen intrinsic coagulation defects; 2. to control heparin administration; 3. in the control of oral anticoagulant treatment. Many different preparations of phospholipid of human, animal and vegetable origin are used as PTT reagents. In addition, different activators, incubation times, concentrations of calcium chloride and test dilutions of plasma and phospholipid are recommended for routine laboratory use. The need to standardise both reagents and technique has been emphasised in many reports. To meet the need for a reference preparation for the PTT test, a large batch of phospholipid material of human brain origin, designated 71/25, was prepared in the National (UK) Reference Laboratory in lyophilised form in 1971 and proposed as a provisional international reference material. This primary master preparation has been used to calibrate subsequent batches of secondary reference preparations distributed to hospitals in the UK and overseas. Results of a number of collaborative studies have demonstrated the greater reliability of the standardised PTT extract compared with commercial extracts used at the same centres in the three aspects of PTT testing. The conclusion to be drawn from these extensive studies of the laboratory and clinical application of the provisional international reference preparation (71/25) is that we may now be in a position to define an acceptable international standard for the APTT.

Administration, Oral↗
PubMed1979

Effects of manufacturing oral contraceptives on blood clotting.

In monitoring the effects of industrial exposure resulting from the pharmaceutical manufacture of oestrogen-progestogen combinations by coagulation studies acceleration of some clotting tests was found. The most pronounced changes were in workers most closely associated with the industrial process. Less pronounced changes were found in women employees not closely concerned with the processing and may have been secondary to the postmenopausal bleeding to which they were prone. A safer work procedure elaborated by the Employment Medical Advisory Service was monitored by clotting studies for over a year but the three most highly exposed subjects showed no substantial improvement.

Blood Coagulation Disorders↗
PubMed1979

Quality control trials of prothrombin time: an assessment of the performance in serial studies.

A series of collaborative exercises on the one-stage prothrombin time test involving hospitals in Britain and overseas was performed between 1972 and 1977. The British Comparative Thromboplastin (BCT) and the lyophilised test plasmas were issued from the National (UK) Reference Laboratory for Anticoagulant Reagents and Control. Participants were asked to test the plasma samples with the BCT using the recommended technique. Variability of performance was assessed by the 'index of reliability' based on the plasma variance and error variance within each exercise. The results show that hospitals have attained higher precision in the later trials.

Humans↗
PubMed1979

Changes in the coagulation of blood during resection of the abdominal aorta.

In 33 patients, a significant fall in the fibrinogen level occurred during an operation to replace the abdominal aorta by a bifurcated prosthesis. There was a similar, but less marked, fall in the fibrinogen level of ten patients having a femoropopliteal vein bypass. A concomitant drop in the plasma plasminogen value was also found. Results of specific laboratory tests for intravascular clotting and activation of fibrinolysis were negative. This suggests that fibrinogen may be removed by physical means. The fall in fibrinogen was so low in some patients that the routine administration of a conventional dosage of heparin could be dangerous.

Adult↗