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PubMed1989

Relationship between arterial and venous activated partial thromboplastin time values in patients after percutaneous transluminal coronary angioplasty.

This quasi-experimental study was conducted to determine whether reliable activated partial thromboplastin time (APTT) values could be obtained from samples taken from indwelling arterial catheter lines. The 30 subjects, who were receiving heparin infusions after a percutaneous transluminal coronary angioplasty (PTCA), had femoral intraarterial lines. With use of a counterbalanced design, APTT values determined in two serial samples of venous and arterial blood were compared for the 30 subjects. The venous blood samples were drawn at the same time as the comparable arterial blood samples. The arterial blood samples were withdrawn after discarding arterial blood equal to four or six times the indwelling catheter volume. A significance level of 0.01 was established to increase statistical control. A histogram was developed from the differences between the arterial and venous blood samples for each of the two groups (four times and six times the discard volume). The histogram indicated that three of the 30 subjects had arterial-venous APTT differences that exceeded 19 seconds when four times the discard volume was used. In the samples where six times the discard volume were used, only one person had an APTT reading greater than 8 seconds. Paired t tests revealed statistically significant differences between the arterial and venous APTT values (t = 2.95, df = 29, p less than 0.01) for discards of four times the catheter dead space volume, whereas no statistically significant difference was found between the arterial and venous APTT values (t = 2.62, df = 28, p greater than 0.01) for discards of six times the dead space volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Activated partial thromboplastin time performed on capillary blood.

Activated partial thromboplastin time is one of the most frequently used assay in haemostasis investigation, but sampling of venous blood is often difficult in newborns (as well as some adult patients). We analysed a method described by Zondag et al [9] performed on capillary blood samples. We studied normal adults and newborns, patients with liver diseases, and those receiving therapy with vitamin K antagonists and heparin. Capillary assay was correlated with venous blood in normal subjects, in patients with liver diseases and during therapy by vitamin K antagonists. However results both in newborns and adults during heparin therapy were not accurate.

Adolescent↗
PubMed1989

[Laboratory controls of heparin therapy with thrombin time, partial thromboplastin time and activated recalcification time].

For the laboratory control of a heparin therapy thrombin time, partial thromboplastin time and activated recalcification time are used. On account of distinct differences in the heparin sensitivity of these reactions an indication-related application is necessary. The ability of evidence and the possibility of establishing test-specific therapeutic regions are restricted by differences caused by reagents, individual variability and influence by accompanying haemostasiological changes. The own approach, taking into consideration the so-called heparin resistance, it presented.

Blood Coagulation Tests↗
PubMed1989

Regional thromboplastin standardisation using a human brain extract.

The preparation, regional distribution and standardisation of an acetone-dried extract of human brain thromboplastin was prospectively evaluated. The programme was shown to be easy to implement within the constraints of the World Health Organisation recommendations and offers a practical alternative to a national standard in countries where the cost of distribution and lack of expertise in preparing such material are limiting factors.

Animals↗
PubMed1989

[Experiences with the use of a lyophilized reference plasma for calibrating the determination of thromboplastin time values].

Experiences are notified about production and employment of a lyophilised standard plasma for designation of thromboplastin time-value in the district Magdeburg. In addition to testing the homogeneity and the methodology for declaration the 100% - value results of ring tests are exhibited, which underline the necessity of a unitary standard plasma pool, secured to various criterions.

Adult↗
PubMed1989

Routine use of the prothrombin and partial thromboplastin times.

The prothrombin time (PT) and activated partial thromboplastin time (APTT) tests are often routinely ordered for hospitalized patients. Ordering patterns and clinical indications for the PT and APTT tests on the medical service at a teaching hospital were studied. Eighty-one percent of all patients admitted to the medical service had a PT and APTT test ordered. When compared with a modified version of guidelines for the use of the PT and APTT tests recently developed by the Medical Necessity Project of the Blue Cross and Blue Shield Associations of America and endorsed by the American College of Physicians, at least 70% of these tests were not clinically indicated. Many of the unindicated tests were ordered prior to invasive procedures or, apparently, out of habit. These inappropriate PT and APTT tests cost at least $60,948 per year for the medical service. Based on these findings, we suggest methods of reducing the inappropriate use of the PT and APTT tests.

Blood Coagulation Tests↗
PubMed1985

A comparison between two commercially available activators for determining the partial thromboplastin time.

Activators that are used to determine the activated partial thromboplastin time should be sensitive enough to detect mild deficiencies of coagulation factors in a reproducible fashion. We compared two commercially available activators--a newly modified preparation of ellagic acid activator and a silica activator. Both reagents produced results that were reproducible over a broad range of concentrations of factors involved in the intrinsic coagulation pathway. The ellagic acid activator was more sensitive in detecting a partial deficiency of nearly all of these factors.

Adult↗
PubMed1988

Effects of reagent and instrument on prothrombin times, activated partial thromboplastin times and patient/control ratios.

Activated partial thromboplastin times accumulated from two proficiency testing surveys were analyzed to determine simultaneously the effects of the method and reagent used. Prothrombin time results were reevaluated concomitantly for comparison. A robust two-way analysis of variance was applied to determine the effect of method and reagent on APTT results. The effect of the reagent and method on the ratio of abnormal to normal plasma clotting times was determined. We found a substantial difference in ratios for the PT using different reagents on the same instrument. There was an even larger effect of reagents on APTT ratios. Our finding of substantial reagent effects for the PT and APTT clearly support the need for standardization. We found standardization to be feasible only for the PT, and only if applied in a form consistent with the inherent error structure of the data. For the APTT, the present methodology and plasma samples did not achieve consistent standardization.

Blood Coagulation Tests↗
PubMed1988

The limited importance of factor Xa inhibition to the anticoagulant property of heparin in thromboplastin-activated plasma.

The antifactor Xa activities of heparin fractions are widely used as an ex vivo index of their antithrombotic efficacy. Its clinical meaning, however, remains speculative. In the study reported, we measured the effects of standard heparin, a synthetic pentasaccharide heparin (antifactor Xa activity only), and a low molecular weight heparin (LMWH) on factor Xa, factor Va, and thrombin generation in thromboplastin-activated plasma. We clearly demonstrated that the antifactor Xa activity of heparin contributed little in its anticoagulant activity. The inhibition of factor Va generation, dependent on the heparin antithrombin activity only, is of prime importance to the inhibition of thrombin generation in plasma. The inhibition of thrombin generation by the LMWH was comparable with that of standard heparin on the basis of their respective antithrombin specific activities, but not on the basis of their antifactor Xa activities.

Blood Platelets↗
PubMed1988

[Activated thromboplastin time, plasma heparin and plasma fibrinogen using the Fibrintimer 10].

After a thorough study, and having chosen the machine that is to equip an average sized haemostasis laboratory, the installation then requires certain steps (the reorganisation of work, better adapted reagents, a change of normality, a fine tuning of the technics, the time to get used to the machine). In this perspective, this work describes the regulation of the technic to determine the heparin activity on the Fibrintimer 10 (F 10) by chronometry (thrombin clotting time with variable concentration), a study of the repeatability and reproducibility of activated partial thromboplastin time (APTT), plasma heparin (HEP) and fibrinogen on the Fibrintimer 10, a study of the correlation between the results we got with the F 10 and the thermostat water-bath for the APTT and the HEP and between those we got on the F 10 and the fibrometer for the fibrinogen. The F 10 has allowed us to save more time whilst keeping the same technics and reagents. The determination of the heparin activity, by thrombin clotting time with variable concentration, gives us a method which is quick, cheap and useful for the following-up of the patients undergoing a treatment with standard heparin. The reproducibility and repeatability prove to be good for the 3 tests in our operatory conditions as well as the correlations between the results we get with both methods.

Adult↗
PubMed1988

[Rare causes of decreased thromboplastin values].

Rare causes of decreases of the thromboplastin time value are hereditary coagulopathies, coagulation inhibitors and application of acetyl salicylic acid. They require a special diagnostic approach including other global and group tests, functional tests of thrombocytes, analyses of individual factors as well as methods of inhibitor proofs.

Blood Coagulation Factors↗
PubMed1988

[Disorders in the contact phase system of blood coagulation as a cause of increased partial thromboplastin time].

Deficiency conditions in the contact phase system of the blood coagulation belong to the rare hereditary defects. Clinically, there is as a rule no inclination to haemorrhage but an increased risk of thrombosis. Therefore, the diagnosis is frequently made on the basis of incidental findings within the framework of routine examinations. Indicating sign is a greatly prolonged partial thromboplastin time (PTT) without clinical signs of haemorrhage. 3 patients with factor XII deficiency are presented and the diagnostic method in prolonged PTT is explained.

Blood Coagulation Tests↗
PubMed1987

Monitoring of heparin therapy with the activated partial thromboplastin time and chromogenic substrate assays.

Heparin therapy was monitored with the activated partial thromboplastin time (APTT) and with chromogenic substrate assays (factor Xa and factor IIa inhibition) in 100 plasma samples from 47 patients. Heparin concentrations were classified as being below, within or above a defined therapeutic range (TR; 0.2-0.55 units heparin/ml). In a first group of patients (A), all three assays allocated the plasma heparin levels to the same concentration interval with respect to the TR. The most frequent diagnoses in group A were uncomplicated arterial or venous thromboembolism, myocardial infarction with limited tissue necrosis, cardiac surgery without major complications and successfully treated infectious disease. In a second group of patients (B), the results of APTT suggested higher heparin concentrations with respect to the TR than the chromogenic assays. Predominant diagnoses were severe infectious diseases, severe liver disorders, extensive myocardial infarction and postoperative complications after cardiac surgery. The discrepancy between heparin concentrations determined by either APTT or the chromogenic substrate assays is most likely due to a non-heparin related prolongation of APTT caused by the underlying disease.

Chromogenic Compounds↗
PubMed1987

Maternally administered antenatal vitamin K1: effect on neonatal prothrombin activity, partial thromboplastin time, and intraventricular hemorrhage.

Infants weighing 1500 g or less at birth are susceptible to intraventricular hemorrhage. This may be due in part to low concentrations of vitamin K-dependent clotting factors. Women in labor between 24-34 weeks' gestation were selected, according to their hospital registration number, to receive 10 mg vitamin K1 intramuscularly at least four hours before delivery. Control women received no vitamin K. The study included only infants born of mothers who were in hospital more than four hours before delivery, who weighed 1500 g or less at birth, and were less than 34 weeks' gestation. Twenty vitamin K1 and 33 control infants qualified for the study. Infants in both groups received routine postnatal vitamin K1. On admission, the infant's prothrombin activity and partial thromboplastin time (PTT) were measured. A head ultrasound was done between days 2 and 4 of life. Results demonstrated significantly improved prothrombin activity, a nonsignificant trend toward improved PTT, and a significantly decreased frequency of intraventricular hemorrhage in infants whose mothers had received vitamin K1. The effect of antenatal vitamin K1 on prothrombin activity and PTT appeared to be more pronounced in female infants.

Blood Coagulation↗
PubMed1987

Monitoring heparin therapy by the activated partial thromboplastin time--the effect of pre-analytical conditions.

Blood and plasma specimens from patients receiving heparin were collected and stored under various conditions. The effect of these conditions on the activated partial thromboplastin time (APTT) was assessed. Four APTT reagents were used. Blood samples centrifuged at 600 X g gave slightly shorter APTTs than samples centrifuged at 940 X g and 2200 X g. Storage of uncentrifuged citrated-blood at room temperature resulted in 15-29% shortening of the APTT, depending on the reagent used. Storage of the same blood samples at 4 degrees C resulted in 6-19% lengthening of the APTT. The presence of HEPES-buffer in citrated-blood shortened the APTT of heparinized patient specimens, but not of normal specimens. When blood was collected in a mixture of citric acid, theophylline, adenosine and dipyridamole (CTAD-mixture), storage at room temperature induced 0-11% decrease of the APTT, depending on the reagent used. Storage of CTAD-blood at 4 degrees C resulted in 7-19% lengthening of the APTT. Shortening of the APTT could be explained by release of platelet factor 4 (PF4). Release of PF4 could be inhibited by CTAD-mixture. These data suggest that storage of CTAD-blood at room temperature is the best pre-analytical condition for reliable monitoring of heparin therapy by the APTT.

Anticoagulants↗
PubMed1987

The effects of heparin on the activated partial thromboplastin time of the College of American Pathologists Survey specimens. Responsiveness, precision, and sample effects.

Heparinized survey samples from the College of American Pathologists from 1981 through 1984 were reviewed to assess effects of the various reagents and instrumentation on the performance of the activated partial thromboplastin time (aPTT) in response to heparin. Responsiveness of the aPTT to the concentration of heparin as well as its sensitivity to the detection of heparin in the therapeutic range was most affected by choice of reagents. Precision was most affected by choice of instruments with photo-optical devices being roughly comparable. A previously described effect of calcium vs sodium salts of heparin was not supported by these data. Survey results were compared with results from fresh plasma samples from patients who had received heparin therapeutically and with response curves obtained from specimens heparinized ex vivo. The pattern of reagent dose responsiveness to the heparinized patient samples differed from that seen with survey samples and with the ex vivo heparinized fresh plasma samples. In addition, intrinsic characteristics of the individual specimens exerted substantial effects on the test results for all specimen types. Therefore, one cannot automatically assume that phenomena that hold for one form of plasma preparation are applicable to another. The nature and source of the heparinized plasma specimen must be taken into account when interpreting aPTT results.

Blood Coagulation Tests↗
PubMed1987

Heparin dosage adjustment in patients with deep-vein thrombosis using heparin concentrations rather than activated partial thromboplastin time.

In patients with deep-vein thrombosis, heparin dosage adjustment based on measurement of heparin concentrations in whole blood was compared with conventional dosage adjustment based solely on activated partial thromboplastin time (APTT) measurement. Initially, all patients were given i.v. bolus doses of heparin sodium 70 units/kg followed by continuous infusion of 16 units/kg/hr. Seventeen patients (group 1) had their initial heparin dosages adjusted according to the results of the APTT value four hours after the start of heparin therapy; subsequent adjustments were made to maintain APTT values within the therapeutic range of 1.5 to 2.5 times the patient's baseline control. Fifteen patients (group 2) had heparin dosage adjusted four hours after the start of heparin infusion, based on apparent heparin clearance using the two-point method of Chiou et al., to maintain whole-blood heparin concentrations of 0.3 to 0.6 units/mL. APTT values less than 1.5 times control occurred in about 12% of group 1 patients at 8, 12, and 24 hours and in 11 of 17 (65%) for at least one value during the study. In group 2 patients, no APTT values were less than 1.5 times control. The patients in group 2 had faster symptomatic improvement and shorter hospital stays. Heparin dosing based on measurement of whole-blood heparin concentrations and application of a practical two-point pharmacokinetic model was superior to dosing based on APTT values.

Adult↗
PubMed1986

Partial thromboplastin time test--proposed performance guidelines. ICSH Panel on the PTT.

The partial thromboplastin time (PTT) test is widely used as a screening test for the detection of hemophilia. It is also used to monitor patients on heparin anticoagulation. This proposal from a ICSH Panel proposes guidelines for the performance of this test, including comparable reference ranges, precision and sensitivity requirements.

Blood Coagulation Tests↗