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Biomedical subjects

A Tripodi

Publications and source records attributed to A Tripodi.

At least 73 records · Page 4Linked to original sources
PubMed1998

Laboratory screening of thrombophilia. Evaluation of the diagnostic efficacy of a global test to detect congenital deficiencies of the protein C anticoagulant pathway.

Clinical laboratories are at present confronted with increasing demands for thrombophilia work-up, which may seriously overwhelm their capacity. Recently, methods able to investigate the protein C anticoagulant pathway globally have been proposed. In this study we investigated the reliability of one such method for its ability to detect patients with known defects of the pathway by testing plasmas from patients with the FVQ506 mutation, with congenital protein C, protein S or antithrombin deficiencies, and patients with previous history of thrombosis, but no identifiable defects. The results show that the new global test fulfils the requirements for congenital protein C deficiency and activated protein C resistance associated with the FVQ506 mutation, which account for more than half of the congenital defects found in thrombophilia. However, congenital protein S deficiency very often remains undetected by this test. Improvement of sensitivity toward this component of the protein C anticoagulant pathway would enroll the global test as a suitable candidate to explore the pathway. Since antithrombin, which also remains undetected by this test, is an additional important risk factor for venous thrombosis, devoting time and effort to developing global tests able to detect defects in both the antithrombin and protein C pathways is warranted.

Activated Protein C Resistance↗
PubMed1998

Three novel PROC gene lesions causing protein C deficiency.

Missense mutations, three of them novel (Asn210-->Val, Asn248-->Ile, Ala355-->Val), were found in the protein C (PROC) genes of 7 patients with inherited protein C deficiency associated with venous thrombosis. Comparison with the phenotypic effects of mutations in the analogous residues of factor IX causing haemophilia B and the use of molecular modelling has provided explanations as to how these lesions might alter either the structure, function or secretion of the protein C molecules encoded.

DNA Mutational Analysis↗
PubMed1998

The importance of "like to like" ISI calibrations with freeze dried plasmas. European Concerted Action on Anticoagulation.

AIM: To assess reliability of like to like and cross species calibrations using two types of certified freeze dried plasma calibrants--artificially depleted of vitamin K clotting factors, and from coumarin treated patients. METHODS: Six ECAA national control laboratories provided certified values for the freeze dried plasmas in terms of the human plain international reference preparation (IRP) (BCT/441) with the manual prothrombin time technique. Eight other ECAA national laboratories determined international sensitivity index (ISI) values in full fresh plasma same species and cross species WHO calibrations against a low ISI human IRP (BCT/441) of the ECAA low ISI human thromboplastin and high ISI ECAA rabbit thromboplastin. Parallel calibrations were performed using the certified values. RESULTS: Calibrations on fresh plasmas of the human ECAA reference thromboplastin (stated ISI = 0.95) gave ISI of 0.957 against the human IRP and 1.66 against the rabbit IRP. The ECAA rabbit (stated ISI = 1.67) gave an identical value on the fresh plasma calibration v the human IRP. With freeze dried depleted plasmas certified in terms of the human IRP, the ISI of the ECAA human was 1.01, but the ECAA rabbit (stated ISI = 1.67) gave a low ISI of 1.47. The freeze dried coumarin plasmas gave an ISI of 0.943 for the ECAA human but only 1.493 for the ECAA rabbit. CONCLUSIONS: Fresh plasmas give reliable ISI when calibrating thromboplastins in same species and cross species calibrations. Freeze dried plasmas certified in terms of a single IRP, whether artificially depleted or of coumarin plasma origin, cannot be used for calibration of dissimilar thromboplastins.

Anticoagulants↗
PubMed1998

Bovine cumulus-corona cells in maturing oocytes. A scanning electron microscopic study.

The ultrastructural features of cumulus-corona cells surrounding maturing oocytes in bovine were studied by means of scanning electron microscope in order to provide a detailed description of their surface changes during oocyte maturation. Cumulus corona cell complexes of immature oocytes showed a compact aspect with narrow intercellular spaces. The spaces around mature oocytes enlarged because they were progressively filled with abundant microfibrillar extracellular matrix. In cumulus corona cells complexes of immature oocytes very numerous long and filiform microvilli were observed, whereas the cumulus corona cell surface surrounding mature oocytes showed occasional large cytoplasmic protrusions along with scanty microvilli and numerous blebs.

Animals↗
PubMed1998

The European Concerted Action on Anticoagulation (ECAA) evaluation of a set of lyophilized normal plasmas to establish the normal prothrombin time for coagulometer systems.

Establishing the mean normal prothrombin time (MNPT) from fresh samples for prothrombin ratios and INR often presents difficulty in selection and collection of donors. A set of seven lyophilized normal plasmas has therefore been prepared at the ECAA Central Facility and studied at 143 laboratories in sixteen European states using coagulometers in serial field exercises. All centres tested either the high ISI ECAA rabbit or low ISI ECAA human reference thromboplastin. The MNPT of fresh plasmas and means of the lyophilized samples were closely comparable with most routine rabbit thromboplastins. Using human thromboplastins means with the lyophilized normals were marginally but significantly longer and with the bovine Thrombotest significantly shorter than the MNPT of fresh plasmas causing alterations in INR. There was no appreciable effect on INR of 2.5 and 3.5 when lyophilized normals were substituted for fresh normals with the rabbit reagents.

Animals↗
PubMed1998

International collaborative study for the calibration of a proposed reference preparation for thromboplastin, human recombinant, plain. On behalf of the Subcommittee on Control of Anticoagulation.

Stocks of the International Reference Preparation (IRP) for thromboplastin, human, plain, coded BCT/253 and held by the World Health Organization (WHO) are nearly exhausted and must be replaced. For practical reasons the choice of the replacement candidate was restricted to two available human recombinant preparations which were coded as X/95 and Y/95 and calibrated in an international collaborative study involving 19 laboratories from Europe, Australia, Canada and Argentina. To minimize the differences between routes of calibration, the two candidates were calibrated against the existing WHO-IRP from human, rabbit and bovine origin and the final ISI was the resultant average value. On the basis of predefined criteria (i.e., within- and between-laboratory precision of the calibration and the conformity to the calibration model), X/95 was the preferred candidate. The assigned ISI (SE of the mean) value is 0.940 (0.0060) and the interlaboratory coefficient of variation 4.7%.

Animals↗
PubMed1998

Standardization of the APC resistance test. Effects of normalization of results by means of pooled normal plasma.

Results for APC resistance tests are expressed as the ratio of the clotting time with and without APC (APC ratio). Normalization by dividing the patient's APC ratio by that of the pooled normal plasma (PNP) (n-APC ratio) was proposed to minimize between-lot reagent variability. To evaluate the merits of different expressions of the results, sets of 80 coded frozen plasmas from carriers (n = 30), non-carriers (n = 30) of the FV:Q506 mutation and 10 copies each of two control plasmas were sent to 7 expert laboratories which were asked to assess APC resistance by their methods. Results were expressed as APC ratio and n-APC ratio by the local PNP and 2 common PNP (A and B). These contained plasmas from the same (n = 20) non-carriers. In PNP A, plasma from one non-carrier was replaced with that from one heterozygous carrier. The merits of different expression of results were judged by (i) within-laboratory reproducibility: (ii) discrimination of carriers from non-carriers: (iii) between-method comparability of results. The influence of FV:Q506 plasma in the preparation of PNP was also assessed. Reproducibility, generally good even with results expressed as APC ratio (median CV 4.6% and 3.0% for normal and abnormal control), was not changed by normalization. Discrimination did not change whatever the method of result expression. Between-method comparability of results was scarcely affected by normalization with the local PNP, whereas it was considerably improved after normalization with the common PNP, but only for the non-carriers. APC ratios for PNP A by all methods were significantly lower than those for PNP B. Thus, the presence of mutant FV in a proportion as low as 2.5% may reduce the APC ratio of the PNP.

Blood Coagulation Tests↗
PubMed1998

Changes of prothrombin fragment 1+2 (F 1+2) as a function of increasing intensity of oral anticoagulation--considerations on the suitability of F 1+2 to monitor oral anticoagulant treatment.

Plasma F 1+2 levels, the activation peptide originating from the factor Xa-mediated activation of prothrombin, increase in many clinical conditions associated with hypercoagulability and decrease in patients on oral anticoagulant treatment (OAT). However. the usefulness of F 1+2 measurement to monitor OAT has not yet been investigated in clinical studies. Before those studies are attempted, the plausibility of its implementation in the laboratory control of OAT should be evaluated. In this respect, a thorough investigation of the pattern of changes of F 1+2 as a function of increased intensity of anticoagulation expressed as International Normalized Ratio is essential. One hundred and thirty-two patients on long-term warfarin treatment were recruited to cover 8 ranges of anticoagulation from < 1.5 to 9.0 INR. F 1+2 was measured in batch on frozen plasma and INR was determined on fresh plasma. The relationship of F 1+2 vs. INR showed a hyperbolic pattern with F 1+2 levels decreasing progressively and significantly as a function of increasing INR up to 3.0. A further decrease in F 1+2 levels observed at INR up to 4.0 was not statistically significant. At INR greater than 4.0, F 1+2 reached a plateau, with mean levels not significantly different for patients at increasing INR up to 9.0. Since the risk of bleeding increases at INR greater than 4.5, our results suggest that F 1+2 is of little value to assess the hemorrhagic risk in patients on OAT.

Administration, Oral↗
PubMed1998

Assessment of the influence of citrate concentration on the International Normalized Ratio (INR) determined with twelve reagent-instrument combinations.

Citrate concentration is one of the variables that can affect coagulation tests. However, few studies have so far been performed to assess the magnitude of this effect on coagulation tests in general and PT in particular. The aim of this study was to assess the extent of influence of citrate concentration on the PT test with results expressed as INR. Twelve reagent-instrument combinations (systems) were calibrated vs. the Reference Preparation BCT/441 using plasmas collected in either 105 mM or 129 mM citrate from normals and anticoagulated patients (OAT). PTs for plasmas collected in 129 mM citrate were longer than those collected in 105 mM both for normals and patients on OAT, but the ratios (patient-to-normal clotting times) for the two citrate concentrations were significantly different in many instances, implying that the International Sensitivity Index (ISI) is also different. ISIs for calibrations with plasmas collected in 105 mM were greater (up to 10%) than those with plasmas collected in 129 mM citrate. When PT ratios were transformed into INR using crossover ISIs (i.e., plasmas collected in 105 mM and ISI determined with plasmas collected in 129 mM citrate, or vice versa) we found that an INR of 4.5 could be up to 20% apart from the value that would have been obtained if the appropriate ISI was used. Moreover, if the ISI determined with the manual technique was used to convert PTs obtained with a particular instrument into INR, the effect of citrate concentration was even greater (INR difference up to 64%). Should these observations be valid for other systems, they might provide additional explanations for the frequent reports which document discrepancies in the INR determined with different systems to which incorrect ISI might have been applied. World-wide consensus on a single citrate concentration to collect patients' as well as lyophilized plasmas to be used in External Quality Assessment Schemes and for local system calibration is therefore urgently needed.

Blood Coagulation Tests↗
PubMed1998

The European Concerted Action on Anticoagulation (ECAA): field studies of coagulometer effects on the ISI of ECAA thromboplastins.

Local calibration studies have been performed with lyophilized plasmas at 155 European laboratories to assess coagulometer effects on manual ISI of ECAA thromboplastins (low ISI human recombinant and high ISI rabbit brain). Common sets of 7 normal and 20 artificially depleted lyophilized plasmas were tested with the thromboplastins in the routine local coagulometers. With the human reagent, marked lowering of the manual ISI resulted with most coagulometers, which was associated with disproportionate shortening of the normals. Where this shortening did not occur, there was little coagulometer effect on the ISI. With the rabbit reagent, proportionate shortening with both normal and abnormal plasmas occurred in most instruments with little effect on ISI. INR correction by local ISI assignment appeared successful with the ECAA human reagent. There was negligible INR correction from local calibration of the ECAA rabbit reagent in coagulometers where thromboplastin ISI were unchanged from the ECAA established manual values.

Animals↗
PubMed1998

Combined use of single and double-cross steel wires for closure of midline sternotomy.

BACKGROUND: We describe an improved technique for sternal closure which is performed using combined single and double-cross steel wires. We made a mechanical study of these single and double-cross shapes considering the effects of applied transverse and longitudinal shearing forces. METHODS: We used this technique in 80 patients who underwent coronary surgery with the use of bilateral internal mammary arteries. RESULTS: Among them no major wound complications occurred, and in all cases a firm stabilization of the sternum was achieved. CONCLUSIONS: We therefore consider this technique of sternal closure easy, safe and effective, also in patients considered at risk for sternal dehiscence.

Bone Wires↗
PubMed1997

A simplified statistical method for local INR using linear regression. European Concerted Action on Anticoagulation.

A simplified method of International Normalized Ratio (INR) derivation using linear regression of certified INR plotted against local prothrombin time (PT) results has been compared with INR from conventional orthogonal regression. Linear regression assumes error only with the local PT results whereas orthogonal regression assumes error with both reference and local results. The reliability of local INR derivation using lyophilized plasmas has been assessed in a collaborative study. INR from conventional fresh plasma International Sensitivity Index (ISI) calibrations have been compared with INR from calibrations with two types of lyophilized plasma, artificially depleted and coumarin. Although calibration slopes differed with the two types of analysis and the different lyophilized plasmas, both gave reasonable approximations to fresh plasma ISI calibrations. With orthogonal regression the overall percentage INR deviation was 5.25% with the artificially depleted plasmas and 6.85% for the results with lyophilized coumarins. With the linear regression, deviation was 8.40% for the artificially depleted plasmas and 5.05% for coumarin-treated patients' lyophilised-plasma. The simpler regression method appears to be worthy of further study as the present report has demonstrated that if the calibrant plasmas are accurately certified with the thromboplastin International Reference Plasma (IRP) results approximate to the conventionally determined INR using the manual PT technique. Coagulometers require further assessment.

Blood Coagulation Tests↗
PubMed1997

Screening for the FV:Q506 mutation--evaluation of thirteen plasma-based methods for their diagnostic efficacy in comparison with DNA analysis.

The factor V (FV) mutation Q506 that causes resistance to activated protein C (APC) is the genetic defect associated most frequently with venous thrombosis. The laboratory diagnosis can be made by DNA analysis or by clotting tests that measure the degree of prolongation of plasma clotting time upon addition of APC. Home-made and commercial methods are available but no comparative evaluation of their diagnostic efficacy has so far been reported. Eighty frozen coded plasma samples from carriers and non-carriers of the FV:Q506 mutation, diagnosed by DNA analysis, were sent to 8 experienced laboratories that were asked to analyze these samples in blind with their own APC resistance tests. The APTT methods were highly variable in their capacity to discriminate between carriers and non-carriers but this capacity increased dramatically when samples were diluted with FV-deficient plasma before analysis, bringing the sensitivity and specificity of these tests to 100%. The best discrimination was obtained with methods in which fibrin formation is triggered by the addition of activated factor X or Russell viper venom. In conclusion, this study provides evidence that some coagulation tests are able to distinguish carriers of the FV:Q506 mutation from non-carriers as well as the DNA test. They are inexpensive and easy to perform. Their use in large-scale clinical trials should be of help to determine the medical and economic benefits of screening healthy individuals for the mutation before they are exposed to such risk factors for venous thrombosis as surgery, pregnancy and oral contraceptives.

Anticoagulants↗
PubMed1997

Determination of the International Sensitivity Index of a new near-patient testing device to monitor oral anticoagulant therapy--overview of the assessment of conformity to the calibration model.

A key issue for the reliable use of new devices for the laboratory control of oral anticoagulant therapy with the INR is their conformity to the calibration model. In the past, their adequacy has mostly been assessed empirically without reference to the calibration model and the use of International Reference Preparations (IRP) for thromboplastin. In this study we reviewed the requirements to be fulfilled and applied them to the calibration of a new near-patient testing device (TAS, Cardiovascular Diagnostics) which uses thromboplastin-containing test cards for determination of the INR. On each of 10 working days citrated whole blood and plasma samples were obtained from 2 healthy subjects and 6 patients on oral anticoagulants. PT testing on whole blood and plasma was done with the TAS and parallel testing for plasma by the manual technique with the IRP CRM 149S. Conformity to the calibration model was judged satisfactory if the following requirements were met: (i) there was a linear relationship between paired log-PTs (TAS vs CRM 149S); (ii) the regression line drawn through patients data points, passed through those of normals; (iii) the precision of the calibration expressed as the CV of the slope was <3%. A good linear relationship was observed for calibration plots for plasma and whole blood (r = 0.98). Regression lines drawn through patients data points, passed through those of normals. The CVs of the slope were in both cases 2.2% and the ISIs were 0.965 and 1.000 for whole blood and plasma. In conclusion, our study shows that near-patient testing devices can be considered reliable tools to measure INR in patients on oral anticoagulants and provides guidelines for their evaluation.

Administration, Oral↗
PubMed1996

Effect of tamoxifen on measurements of hemostasis in healthy women.

BACKGROUND: Tamoxifen citrate is being evaluated for primary prevention of breast cancer, but this drug with estrogen-like properties may cause changes in the hemostatic system that would increase the risk of thrombosis. METHODS: Women who had undergone hysterectomy were consecutively enrolled in the placebo-controlled, randomized, double-blind Breast Carcinoma Chemoprevention Tamoxifen Study, which was designed to evaluate the efficacy of oral tamoxifen citrate (20 mg/d). Our substudy of hemostasis and lipid measurements included the first 68 consecutive women assigned to tamoxifen (n = 31) or placebo (n = 37). Blood specimens were obtained before treatment and after 1,2,4, and 6 months of treatment. Measurements included blood cell counts, lipid levels, coagulation activation markers, clotting factors, and anticoagulant and fibrinolysis proteins. RESULTS: Hematocrit and hemoglobin and platelet levels fell slightly but significantly in women treated with tamoxifen. No between-treatment differences were observed in any of the clotting factors. Naturally occurring anticoagulant proteins such as antithrombin and protein C fell slightly in women treated with tamoxifen. However, no significant changes were observed in any of the markers of activated coagulation or fibrinolysis (fibrinopeptide A, prothrombin fragment 1 + 2, thrombin-antithrombin complex, D-dimer). Total and low-density lipoprotein cholesterol levels fell significantly in women treated with tamoxifen. CONCLUSIONS: Tamoxifen induced a modest decrease in anticoagulant proteins, but without biochemical signs of activation of coagulation and fibrinolysis. Tamoxifen improved the lipid profile and induced changes in blood cell counts, which should determine an improvement in blood rheologic factors. These preliminary findings seem to justify continuation of the double-blind study in healthy women, but only direct comparison of thromboembolic complications in the 2 treatment groups will establish whether tamoxifen carries a risk of thrombosis.

Administration, Oral↗
PubMed1996

Mechanisms, markers and management of hypercoagulable states.

Information on hypercoagulability can be achieved through the measurement of peptides that are generated when zymogens are activated, of the active enzymes, or of the complexes that form in the circulation when enzymes are inactivated by their plasmatic inhibitors. These assay methods have dramatically improved our understanding of the mechanisms which regulate coagulation in health and disease. However, their choice and use as predictors of thrombotic events and to monitor anticoagulant treatment still need to be defined in prospective clinical trials.

Biomarkers↗