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Biomedical subjects

L Poller

Publications and source records attributed to L Poller.

At least 127 records · Page 7Linked to original sources
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↗
PubMed1978

Oral anticoagulants controlled by the British comparative thromboplastin versus low-dose heparin in prophylaxis of deep vein thrombosis.

The British comparative thromboplastin (BCT) was used to monitor the effectiveness of oral anticoagulants in preventing deep vein thrombosis (DVT) in patients undergoing major gynaecological surgery. All patients were screened for DVT with the use of the (125)I-fibrinogen scan.One hundred and forty-five patients aged 40 years or more were randomised into three groups. Group 1 received oral anticoagulant (nicoumalone) treatment, stabilised over five days before surgery and continuing into the second postoperative week. The other patients served as two contrast groups and were managed on a double-blind basis. Group 2 received a subcutaneous low-dose regimen of heparin calcium. Group 3 received subcutaneous saline. Eleven of 48 patients in the saline group, three of 49 patients in the heparin group, and three of 48 patients in the oral anticoagulant group developed DVT as judged by (125)I-fibrinogen scanning. The incidences in groups 1 and 2 were significantly lower than in the saline group. The falls in haemoglobin concentration and incidence of haemorrhage were similar in all three groups.The study showed that oral anticoagulant prophylaxis stabilised preoperatively and low-dose heparin were equally effective in preventing deep vein thrombosis in a moderate-risk group. Immediate preoperative prothrombin ratios of 2.0-2.5 and postoperative ratios of 2.0-4.0 with the BCT gave adequate protection without increased haemorrhagic risk.

Acenocoumarol↗