Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Prothrombin Time”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 217 records · Page 12Linked to original sources
PubMed1991

[Standardized prothrombin time determinations and optimal anticoagulant therapy].

WHO and other international organizations have recommended the introduction of a standardized prothrombin time determination. This would allow a universal scale for the intensity of oral anticoagulation therapy to be used. A prerequisite is the use of thromboplastin, calibrated against the international reference thromboplastin, standardized methodology etc. This permits every prothrombin time determination to be expressed as International Normalized Ratio (INR). The introduction of INR facilitates the implementation of optimal oral anticoagulation as defined by larged international studies.

Anticoagulants↗
PubMed1997

Single or duplicate analysis for automated prothrombin time and activated partial thromboplastin time?

The introduction of automated coagulation analysers raises the possibility of performing routine coagulation tests as single rather than duplicate analyses. This study compares the duplicate results of the prothrombin time (PT) and activated partial thromboplastin time (aPTT) to that of a single result obtained by the MLA Electra 1000c using two different methods. The first method looks specifically at the difference between the mean duplicate result and the single result to determine if they alter patient management. This method found that two of 4152 PTs (0.048%) and two of 3047 aPTTs (0.065%) were clinically significant. The second method statistically assessed the agreement between the traditional mean duplicate result and the single test. This supported the introduction of single testing as the calculated 95% confidence intervals demonstrate that each result is interchangeable for purposes of clinical interpretation. These results supported the introduction of single testing for PT and aPTT estimation in our laboratory. The introduction of single testing was accompanied by changes to quality control and machine maintenance to ensure that the functions previously covered by duplicate testing were maintained. A strict protocol for repeat testing has also been adopted.

Australia↗
PubMed1987

Effect of latamoxef on platelet function and prothrombin time in partially nephrectomized rats.

Latamoxef (daily 100 and 300 mg/kg, i.v.) was injected once a day for 8 days to 75% and 90% nephrectomized rats kept on a vitamin K-sufficient diet (500-600 ng/g) or a vitamin K-deficient diet (30-50 ng/g), and changes in ADP-induced platelet aggregation and prothrombin time were examined. The half-life of latamoxef was markedly prolonged and plasma latamoxef and N-methyltetrazolethiol (NMTT) concentrations increased, resulting in a delay of the total body clearance of the compounds. The ADP-induced platelet aggregation increased after nephrectomy, and latamoxef slightly but inconsistently decreased the aggregation. Prothrombin time did not change even in the 90% nephrectomized rats kept on an ordinary diet, but increased dose-dependently in the vitamin K-deficient nephrectomized rats, with the 90% nephrectomized animals showing larger increases of prothrombin time. These data suggest that NMTT or NMTT-containing antibiotics cause no hypoprothrombinemia even in partially nephrectomized rats when they are fed an ordinary diet containing vitamin K, but these compounds enhance the manifestation of hypoprothrombinemia in vitamin K deficiency. Further renal failure promotes the manifestation by increasing drug concentration in the blood. However, platelet aggregation in these animals is not significantly affected at the doses examined.

Adenosine Diphosphate↗
PubMed1995

Changes in the prothrombin time, haematology and serum proteins during experimental aflatoxicosis in hens and broiler chickens.

Two groups of 32 laying hens and two groups of 32, 23-day-old broiler chickens were given 2.5 and 5 mg kg-1 of aflatoxin in their diet for four, eight, 16 and 32 days; 16 hens and 32 broiler chicks served as control groups. In the laying hens, aflatoxicosis was characterised mainly by an increase in prothrombin time, and decreases in total plasma proteins and albumin levels; there were increases in red blood cell (RBC) counts and haematocrit which were greater in the group fed 5 mg kg-1. There was a decrease in beta-globulins and an increase in gamma-globulins. In the broiler chickens, there was only a slight increase in prothrombin time and a decrease in RBC counts. This data proves the good sensitivity and utility of prothrombin time values as an indicator of aflatoxicosis in birds.

Aflatoxins↗
PubMed2003

Biochemical markers of fibrosis in patients with chronic hepatitis C: a comparison with prothrombin time, platelet count, and age-platelet index.

As an alternative to liver biopsy, an index of five biochemical markers (alpha2-macroglobulin, apolipoprotein A1, haptoglobin, total bilirubin, gamma-glutamyl-transpeptidase) has been shown to predict the severity of hepatitis C-related fibrosis. The objective of this study was to compare this index with other markers frequently used for this purpose (prothrombin time, platelets, age-platelet index). In 323 hepatitis C-infected patients, the discriminative values of these markers for F2-F4 fibrosis (by the METAVIR classification) were compared. By multiple logistic regression analysis, only the five-marker index (P < 0.0001) and prothrombin time (P = 0.02) were independently predictive of F2-F4 fibrosis. For this outcome, the area under the receiver operating characteristic curve was significantly higher for the five-marker index (0.836 +/- 0.024) than the age-platelet index (P = 0.002), and the platelet count and prothrombin time (P < 0.001), indicating greater diagnostic value. The addition of the latter markers to the five-marker index proved unhelpful for increasing its accuracy. In conclusion, an index of five biochemical markers accurately predicts significant hepatitis C-related fibrosis and is superior to traditional markers.

Adult↗
PubMed2000

Whole blood prothrombin time using diluted tissue factor is shortened in spontaneous hypertensive rats.

Clinical screening tests for blood coagulation that use plasma as samples cannot estimate the participation of platelets, leukocytes, and erythrocytes in blood coagulation system. We developed an assay to evaluate the total coagulation ability of blood and whole blood prothrombin time (WPT) using the principle of prothrombin time with the diluted-tissue factor as a trigger and a newly developed apparatus, STA, viscosity change detection system (electromagnetic clot detection). The activation of platelets by Ca ionophore shortened WPT and increased the expression of CD62P on the platelet surface. WPTs in citrated blood of spontaneous hypertensive rats (SHR) were significantly shorter than those of controls, Wistar Kyoto rats (WKY). Plasma levels of thrombin-antithrombin III (TAT) in SHR were significantly higher than those of WKY. Moreover, WPT and TAT levels were significantly correlated. Based on these results, WPT was found to be useful to estimate the activation of blood coagulation in whole blood.

Animals↗
PubMed1989

Effect of automation on prothrombin time test in NEQAS surveys.

The performance of coagulometers in the National Quality Assessment Scheme (NEQAS) surveys of the prothrombin time conducted between 1986 and 1987 was reviewed. There were sufficient data for analysis for eight types of coagulometer used with a single type of thromboplastin reagent and one instrument with an alternative reagent. The overall reliability efficacy of each instrument was evaluated by determining the orthogonal regression slope parameters for prothrombin time (PT) and international normalised ratios (INR) using the manual technique as the reference method. Seven of the eight types of coagulometer tended to overestimate the INR. A pattern frequently observed with coagulometers, and difficult to regulate, was a trend to underestimate INR below 3.0 and overestimate higher INR. Overestimation of INR values over 3.0 was particularly pronounced with three types of instrument (Fibrintimer, Lancer, KC4/10). The KC4/10 was used by a sufficient number of participants to permit analysis of the performance of individual instruments. Within instrument differences were similar to those produced by different types of coagulometers. Thromboplastin reagents affected the INR values obtained with coagulometers. The study indicates that each local reagent-instrument combination must be calibrated by the participant to obtain reliable INR values. The use of a general correction factor for a local PT system seems to be invalid owing to the considerable variation in performance of individual coagulometers. The two best guides to the choice of coagulometer may be the deviation from the manual result and precision estimated by the coefficient of variation of the INR.

Blood Coagulation Tests↗
PubMed1988

Automation of the prothrombin time assay on a centrifugal analyser using two different chromogenic substrate reagents.

Methods employing chromogenic substrates for the photometric determination of prothrombin time have several advantages over conventional coagulometric methods. We evaluated the analytical qualities of two recently introduced reagents for the photometric determination of prothrombin time. The assays were performed on a centrifugal analyser. Both reagents showed good precision, even with sample volumes of 10 microliters or 12 microliters. The stability of the reagents during storage was investigated at 4 degrees C, 25 degrees C and 37 degrees C. The chromogenic reagent, which contains thromboplastin from human placenta, was compared with a coagulometric method, which includes ox-brain thromboplastin: coagulation activities calculated from International Normalized Ratio values showed good correlation and conformity over the whole test range. The other chromogenic reagent contains thromboplastin from rabbit brain; outside the therapeutic range for oral anticoagulation the results obtained with this reagent showed poor agreement with those obtained with the coagulometric method. Both chromogenic reagents were sensitive to reduced concentrations of coagulation factors of the extrinsic pathway and nearly insensitive to low factor IX concentrations. The results of the photometric test paralleled those of the clotting method during oral anticoagulation therapy.

Centrifugation↗
PubMed1987

Use of a centrifugal analyzer for a chromogenic prothrombin time, a chromogenic activated partial thromboplastin time and a kinetic fibrinogen assay in a routine hospital laboratory.

A Cobas Bio centrifugal analyzer was used in a clinical laboratory for the performance of chromogenic clotting assays. Three commercially available photometric clotting tests--prothrombin time (PT), activated partial thromboplastin time (aPTT) and fibrinogen--were compared with the traditional clotting assays during 3 months. No great discrepancies were found between the traditional assays and the new photometric assays. The chromogenic PT could replace the traditional thrombotest, PT and Normotest, because it was sensitive and accurate over a broad range of clotting factor activity. Furthermore the chromogenic PT could be used to discriminate between a decreased clotting activity due to vitamin K deficiency or to a decreased protein synthesis by the liver. A decreased protein synthesis was confirmed by measuring a decrease in the serum cholinesterase activity. The chromogenic aPTT could be used for the assay of heparin concentrations in the therapeutic range and turned out to be more sensitive for deficiencies of factor VIII and factor IX than a traditional clotting aPTT. We conclude that the accuracy and practicability of clotting assays are improved by the new assays without diminishing the clinical value of the results.

Blood Coagulation Tests↗
PubMed1980

[Study of present possibilities of interlaboratory standardisation of the prothrombin time (author's transl)].

The graphs or tables proposed by the manufacturer of reagents, the Thivolle straight lines suggested by Raby or, since 1977, Loeliger's procedure, are three possibilities offered to biologists to transform the prothrombin time into prothrombin concentrations expressed as a percentage. We have studied the possibility of interlaboratory standardisation in the case of patients treated with coumarin derivatives: firstly with the same thromboplastin under various conditions of use; secondly with five different thromboplastins under identical conditions (choosing arbitrarily one of the reagents as reference). Loeliger's procedure is the one which permits the best standardisation, but its practical application seems difficult. It seems to us that before carrying out this standardisation between laboratories, one should indicate, with the result found for the patient, the area of therapeutic activity of the thromboplastin used, as suggested by Ducker and Marbet in 1977 (these authors determined this area of therapeutic activity for 13 different reagents used in Switzerland).

Coumarins↗
PubMedDate not supplied

Accuracy, clinical correlation, and patient acceptance of two handheld prothrombin time monitoring devices in the ambulatory setting.

OBJECTIVE: To evaluate the accuracy, clinical correlation, ease of use, and patient acceptance of the Coaguchek and the ProTime Microcoagulation System as compared with standard laboratory methods for prothrombin time determination. METHODS: A total of 30 prothrombin times, expressed as international normalized ratios (INRs), were determined by each handheld device for comparison with standard laboratory testing. Accuracy was evaluated by calculating the absolute difference for each pair of INR values. Clinical correlation was defined as an INR obtained by the handheld monitor that would have resulted in the same therapeutic decision as the INR obtained by the standard laboratory method. Subjects were surveyed to determine which method of INR determination they preferred and their reasons for that preference. RESULTS: Accuracy was superior with the Coaguchek monitor. The absolute difference (mean +/- SD) in the laboratory and Coaguchek INRs was 0.28+/-0.23 (p = 0.96). The absolute difference (mean +/- SD) in the laboratory and the ProTime Microcoagulation System INRs was 0.56+/-0.34 (p < 0.001). For clinical correlation, two out of 24 (8.3%) INRs with the Coaguchek were sufficiently different from the laboratory INR to have resulted in a different therapeutic decision, compared with 12 out of 24 (50%) with the ProTime Microcoagulation System (p < 0.005). Of subjects surveyed, 77.8% preferred the finger stick method. CONCLUSIONS: The Coaguchek was superior to the ProTime Microcoagulation System in accuracy, clinical correlation, and ease of use. The study also showed that patients preferred capillary blood sampling by finger puncture over venipuncture for INR monitoring.

Anticoagulants↗
PubMed1980

Antithrombin III contribution to cholestasis differential diagnosis: its correlation with one stage prothrombin time and factor V.

Levels of antithrombin III (AT III) measured by two different methods, Factor V (FV) and One Stage Prothrombin Time, have been studied in two groups of patients: 55 with chronic liver disease and 22 with extra hepatic cholestasis. Results show a statistically significant correlation between the decrease of AT III and FV in the first group, and the normality of these parameters (unrelated to One Stage Prothrombin Time) in the second group. Levels at AT III and FV correlate directly with the functional integrity of hepatic parenchyma, so they may help in the differential diagnosis of different types of cholestasis.

Antithrombin III↗
PubMed1993

[A basic study on a highly sensitive automated method for hypercoagulable state in plasma, fluorogenic prothrombin time (FPT) method].

A highly sensitive automated method, fluorogenic prothrombin time (FPT) method, was developed by a combination of a fluorogenic peptide substrate for thrombin and a centrifugal autoanalyzer (Cobas Bio). Using plasmas from stroke patients, we showed that the second reagent containing fluorogenic peptide substrate should be mixed after the first reagent containing tissue factor and plasma were mixed, that is, two steps method, in order to detect hypercoagulable state. When the first and the second reagent were mixed with plasma at the same time, that is, one step method, FPT was not sensitive to hypercoagulable state. We also showed that patient plasmas should be stored at -80 degrees C and subjected to FPT analysis immediately after thawing, not leaving at 4 degrees C or room temperature. Good correlation was observed on FPT of stroke patients using human tissue factor and bovine tissue factor. Another fluorogenic method was developed by the same principle for the evaluation of factors X and VII concentrations in plasma using deficient plasma of factor X or factor VII. Good correlation was observed on factors X and VII concentrations of stroke patients using human tissue factor and bovine tissue factor.

Blood Coagulation Tests↗
PubMed1983

Calibration of reference thromboplastins and standardisation of the prothrombin time ratio.

Thromboplastins vary in their sensitivity to the haemostatic defect induced by oral anticoagulants. To provide a means of standardising prothrombin time tests, the World Health Organization adopted in 1977 a scheme for calibrating thromboplastins in terms of an International Reference Preparation. Unfortunately, the model on which this scheme was based does not always hold. A revised calibration model has therefore been developed and this has been tested in a recent collaborative study. The revised model, which retains fundamentally the same principle for standardising prothrombin time tests, has proved suitable for calibrating thromboplastins of different species and types and, moreover, has certain statistical advantages over its predecessor. In September 1982, the WHO Expert Committee on Biological Standardization adopted the revised model. This paper explains the nature and rationale of this change and considers its practical implications.

Blood Coagulation Disorders↗
PubMed1997

Optimization of prothrombin time measurements in canine plasma.

OBJECTIVE: To optimize a prothrombin time (PT) method designed for human plasma for use with canine plasma. SAMPLE POPULATION: 100 plasma samples from healthy dogs and 50 plasma samples with reduced activity of the single factors II, V, VII or X. PROCEDURE: Canine plasma samples with various coagulation activity values (100, 75, 50, 25 and 10%: prepared by dilution from a plasma pool [n = 100]) were assayed at various sample dilutions and dilutions of the thromboplastin component of 3 commercial calcium thromboplastin reagents. The sc-named optimized PT test was compared with the standard test with respect to its sensitivity and correlation with the sum of the activity decreases of single factors II, V, VII, and X in relation to the respective reference range. RESULTS: The time intervals between various coagulation activity values, which were small by use of the standard test, could be increased by diluting the sample and substituting fibrinogen, but not by diluting the tissue thromboplastin component of PT reagent. On the basis of 50 abnormal plasma samples, the optimized test had high sensitivity (0.90 to 1.00, dependent on reagent and sample dilution) in contrast to the standard test, which had low sensitivity (0.24 to 0.58, dependent on reagent). Also, correlation with the sum of the activity decreases was closer by use of the optimized (0.90 to 0.93) than the standard (0.58 to 0.84) test. CONCLUSIONS: In contrast to the standard test, an optimized test is suitable as a sensitive screening test of the extrinsic coagulation system in dogs. CLINICAL RELEVANCE: The optimized PT method is easy to perform and, therefore, should be in general use for assay of canine plasma.

Animals↗
PubMed1995

Home monitoring of warfarin therapy in children with a whole blood prothrombin time monitor.

We prospectively evaluated a capillary whole blood prothrombin time (PT) monitor (Biotrack, Ciba Corning) in an outpatient pediatric anticoagulation clinic (40 clinic patients) and in age-matched healthy subjects (30 control subjects). Subsequently, 23 children requiring warfarin therapy were placed on a home program (home patients) using the PT monitor; their parents were trained and the results followed by clinic staff. The PT results were reported as internationalized normalized ratios (INRs). The laboratory and PT-monitor INR values were similar for the clinic patients and the control subjects (y = 0.76x + 0.38; r = 0.93; p < 0.001). The accuracy of the PT monitor (the difference between INR values and the laboratory INR) was best at an INR of 2.5 to 3.5; 90% of paired INR values were within 0.8 INR units. The average duration of monitoring for home patients was 13 months (range, 2 to 60 months). They had an average of 3 dose measurements (range, 1 to 11 measurements) and 1.8 dose changes (range, 0.6 to 4.5 changes) per month. Of the 599 measurements, 63% were within the therapeutic range, similar to those for clinic patients; the dose requirements were also similar. There was 1 significant bleeding event, a subdural hematoma in a patient with an INR of 4.1, and 1 catheter-related thrombotic event with an INR of 1.2; both children recovered. Of the 23 families, one discontinued home monitoring because of parental discomfort, 2 children died of their primary disease, 6 completed warfarin therapy, and 14 remain on the home program. We conclude that the whole blood PT/INR monitor is safe and offers practical advantages to children requiring anticoagulation.

Adolescent↗