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PubMed1984

The lack of effect of tertiary butylhydroquinone on prothrombin time in male rats.

The potential for tertiary butylhydroquinone (TBHQ) to produce hemorrhagic death similar to that seen after butylated hydroxytoluene (BHT) treatment was tested in male rats. Groups of male rats were given three consecutive daily doses of 380, 760 or 1520 mg/kg/day BHT or 50, 100 or 150 mg/kg TBHQ. Twenty-four hours following the last dose, the rats were killed, blood was taken for prothrombin determinations and gross autopsies were performed. No evidence of hemorrhage was found in any of the animals. BHT caused a significant dose-dependent increase in prothrombin times, while the prothrombin times of the TBHQ rats were comparable to the controls. Since hypoprothrombinemia plays a major role in producing hemorrhagic death, these data indicate that the potential for THBQ to have such an effect is low.

Animals↗
PubMed2001

Prothrombin time ratio is reduced by magnesium contamination in evacuated blood collection tubes.

Magnesium ions were detected in sodium citrate solutions in several lots of evacuated blood collection tubes. The mean concentrations ranged between 1.3 and 1.6 mmol/L. Magnesium was also present in the rubber stoppers of the blood collection tubes and could be leached into the citrate solution. It was shown that magnesium added to citrated plasma shortened the prothrombin time of both coumarin and normal plasma. The effect of magnesium was relatively greater on coumarin than on normal plasma resulting in reduced prothrombin time ratio. Shortening of the prothrombin time was also observed when magnesium chloride was added to dialysed plasma, i.e., in the absence of citrate. These results indicate that magnesium contamination can interfere with accurate INR determination in the control of oral anticoagulant therapy.

Anticoagulants↗
PubMed1989

Home prothrombin time monitoring after the initiation of warfarin therapy. A randomized, prospective study.

STUDY OBJECTIVE: To evaluate the efficacy and accuracy of monitoring prothrombin times at home. DESIGN: Randomized, prospective cohort study. SETTING: Outpatients discharged from a university hospital or a community hospital. PATIENTS: Fifty patients started on warfarin for the first time who demonstrated an ability to use the monitor and who had not achieved a stable response to warfarin in the hospital. INTERVENTION: Oral anticoagulation therapy managed using a portable prothrombin time monitor compared with specialized anticoagulation clinic care. MEASUREMENTS AND MAIN RESULTS: In the 46 patients who completed the 8-week study, the median percentage of time that patients in the home-monitor group (n = 23) were within a range equal to the target prothrombin ratio +/- 0.3, but always above 1.25, was 93%, compared with 75% for patients in the clinic group (n = 23) (P = 0.003). There was no significant difference between groups in the percentage of time above the therapeutic range; however, the percentage of time that patients were subtherapeutic was significantly greater in the clinic group (P less than 0.001). There were no major thromboembolic or hemorrhagic complications in either group. Differences between home monitor measurements and corresponding clinical laboratory measurements using blood samples drawn within 4 hours of the home test were comparable to differences observed between measurements using two different clinical laboratory instruments. CONCLUSIONS: Use of a portable prothrombin time monitor by patients at home is feasible and provides accurate measurements. Patients doing home monitoring achieve superior anticoagulation control compared with those receiving standard anticoagulation clinic care.

Adult↗
PubMed2006

Postoperative changes in prothrombin time following hepatic resection: implications for perioperative analgesia.

Disorders of coagulation may occur after uncomplicated hepatic resection in patients who have normal preoperative coagulation profiles and liver function tests. We present a retrospective study performed in a tertiary care university teaching hospital examining changes in liver function tests and coagulation profiles in patients undergoing hepatic resection. Data were obtained for 124 patients. When compared to the preoperative values, prothrombin times were significantly increased throughout the postoperative period. Prolongation of the prothrombin time was related to both duration of surgery and hepatic resection weight. There was no relationship between prothrombin time and patient age. Disorders of coagulation occur after hepatic resection even in patients who have normal preoperative coagulation and liver function tests. This has implications for anaesthetic practice, particularly when considering the use of an indwelling epidural catheter in patients undergoing hepatic resection.

Analgesia↗
PubMed1998

Prolonged prothrombin time and activated partial thromboplastin time due to underfilled specimen tubes with 109 mmol/L (3.2%) citrate anticoagulant.

Underfilling of specimen tubes containing 129 mmol/L (3.8%) buffered citrate prolongs prothrombin time (PT) and activated partial thromboplastin time (APTT) values. We studied this phenomenon by using 109 mmol/L (3.2%) buffered citrate as the anticoagulant, anticipating some increase in tolerance to underfilling. Venous blood drawn from 12 healthy subjects and 30 patients receiving long-term oral warfarin therapy was mixed with 109 mmol/L buffered citrate solution in proportions equivalent to filling the collection tubes from 52% to 100% of capacity. Accurate PT values were obtained from normal specimens if the tubes were filled to 65% or more of capacity. Accurate PT results in the therapeutic range were obtained only with filling to 80% or more of capacity (using a "moderately sensitive" thromboplastin reagent, International Sensitivity Index [ISI] = 2.06) or 90% or more of capacity (using a "highly sensitive" thromboplastin reagent, ISI = 1.01). In contrast, APTT was much less tolerant to underfilling, with prolonged values observed in most specimens filled to less than 90% of capacity. No false low values were observed. Specimen tubes should be filled to at least 90% of capacity to avoid falsely elevated PT or APTT results, but values within the reference range may be acceptable even from underfilled tubes.

Adult↗
PubMed1985

A clinical evaluation of automated chromogenic tests as substitutes for conventional prothrombin time and activated partial thromboplastin time tests.

Automated procedures involving a chromogenic substrate sensitive to thrombin-sarcosine-Pro-Arg p-nitroanilide were compared with conventional tests for prothrombin times and activated partial thromboplastin times (APTT) and with specific assays for factors V, VII, VIII, IX, X, XI, and XII. The reproducibility and sensitivity of the chromogenic tests were compared with those of the clotting tests. Further, we have confirmed that the chromogenic test for APTT is sensitive to factor VII deficiency, unlike the clotting test for APTT. This might be an advantage in monitoring orally anticoagulated patients. The ready availability of the automated equipment for performing the chromogenic tests suggests their potential for routine use. However, some discrepant results in certain patients with liver disease and in others with factor VIII inhibitors warrant caution.

Autoanalysis↗
PubMed1979

Prothrombin time after heparin removal. Application to monitoring simultaneous anticoagulation with heparin and coumarins.

Coumarin-anticoagulated plasmas from 31 subjects comprising two study groups were passed through epichlorohydrin triethanolamine cellulose (ECTEOLA) chromatography columns. Group I plasmas, which were run with nothing added, had mean prothrombin times of 21.6 +/- 5.4 sec prior to and 22.4 +/- 5.6 sec following exposure to these columns (r = 0.9449; t = 1.8307, P less than 0.100). The mean prothrombin time for Group II, 18.2 +/- 4.9 sec, lengthened with 5 u/ml heparin to 35.5 +/- 16.2 sec, and returned to 19.2 +/- 5.0 (r = 0.9763) after chromatography. Therefore, it appears that coumarin anticoagulation had no significant influence upon the capacity of ECTEOLA effectively to remove heparin in therapeutic doses. This means that virtually all prothrombin time reagent systems can be employed to monitor concurrent heparin and coumarin anticoagulation. In addition, quality control of the combined technic is simpler, and the technic more sensitive to low levels of fibrinogen and factor V.

Cellulose↗
PubMed2002

[Prothrombin time and its standardization: a potentiality to introduce INR method in criteria for disseminated intravascular coagulation].

Prothrombin time (PT) is widely utilized for evaluation of diseases with single or multiple coagulation factors disorders, such as severe liver dysfunction and disseminated intravascular coagulation (DIC). However, its standardization of reagent and method is not established yet for universal purpose except International Normalized Ratio (INR) for control of oral anticoagulant therapy (OAT). Neither Prothrombin time ratio adapted in Japanese criteria for DIC nor seconds method in criteria reported by the last SSC meeting is corrected between assays, therefore much dependence on these criteria causes risk of misdiagnosis. In order to resolve incoherence of method of PT, we performed this study for introducing INR method to diagnostic criteria for DIC. In our results, sensitivities of two reagents from human tissue factor (TF) to DIC model plasma with middle to low activities of multiple coagulation factors almost equal to plasma from patients with OAC, although other two reagents from rabbit TF show discrepancy of sensitivities between DIC and OAT plasma. These suggest a potentiality to introduce INR system to diagnosis of DIC when human TF is used as a PT reagent. Based on standardization of method, significance of PT in DIC criteria should be reevaluated in worldwide.

Disseminated Intravascular Coagulation↗
PubMed1985

An analysis of the one-stage prothrombin time.

An analysis of the one-stage prothrombin time using thromboplastins highly (Thrombotest) and slightly (Normotest) sensitive to the Pivka (protein induced by vitamin K absence) inhibitor is presented. A one-tenth dilution of blood with 0.1 mol/l Na3 citrate was satisfactory even at an extreme packed cell volume (PCV). Whole blood and plasma were equally satisfactory as test materials; however, their accuracy and precision were greatly improved when a small sample size at a high coagulation activity and a large sample size at a low coagulation activity were used. The PCV correction method which corrected for the different Pivka inhibitor sensitivities of thromboplastins was preferable.

Biomarkers↗
PubMed1996

Prothrombin time in liver failure: time, ratio, activity percentage, or international normalized ratio?

Prothrombin time (PT) is a universal indicator of liver disease severity. However, variability in thromboplastin reagents leads to large interlaboratory differences in PT results. The aim of this study was to determine whether the use of the international normalized ratio (INR) or other modes of expression might achieve PT standardization in patients with liver failure. PT was measured with seven thromboplastin reagents with different sensitivities in plasmas from 27 patients with miscellaneous chronic and acute liver failure and, as a control population, 29 patients on oral anticoagulation therapy. PT was expressed in seconds, ratio, activity percentage, and INR. In patients with liver failure, only activity percentage expression eliminated variability in PT results obtained with the seven thromboplastins while INR, seconds, and ratio values remained significantly different (P < .01). In patients on oral anticoagulant therapy, only INR normalized PT results. We conclude that, in patients with liver failure, INR fails to yield a PT expression independent of the thromboplastin used and only activity percentage expression may provide a common international scale of PT reporting.

Analysis of Variance↗
PubMed2002

[Introduction of international normalized ratio of prothrombin time to evaluate multiple depletions of coagulation factors].

Prothrombin time(PT) is utilized in worldwide as a global coagulation test reflected multiple depletions of coagulation factors in diseases such as severe liver dysfunction and Disseminated Intravascular Coagulation(DIC). However, standardization of regents and result reporting methods are not established yet except International Normalized Ration(INR) for control of oral anticoagulant therapy(OAT). We evaluated whether INR is capable for defect of multiple coagulation factors except OAT, using absorbed plasma and different origins of thromboplastin; human recombinant, human placenta, cultured human cell and rabbit brain. PTs of individual 90 samples(group MC) absorbed with BaSO4 and/or bentnite and 60 samples(group W) from patients with OAT were measured with 20 normal plasmas with respective reagents. Sensitivities of four reagents to plasma of group W and MC were determined respectively against human recombinant thromboplastin(ISI = 1.03). Both of human thromboplastin showed that sensitivity to absorbed plasma was very close to OAT plasma, whereas reductions of sensitivity to 84% and 66% for absorbed plasma were revealed in both of rabbit thromboplastins. Correlations of INRs calculated by two different sensitivities, one is to absorbed plasma and another to OAT plasma, indicated that discrepancy of sensitivities was emphasized as large slopes(1.50 and 2.76) of regression lines and large intercepts in rabbit thromboplastins, although slopes closed to 1.0 with small intercepts in both of human thromboplastins. We concluded that use of human thromboplastin was the first priority to introduce INR system for evaluation of multiple coagulation factors depletions.

Adult↗
PubMed2004

European concerted action on anticoagulation. Quality assessment of the CoaguChek Mini and TAS PT-NC point-of-care whole-blood prothrombin time monitors.

BACKGROUND: International Normalized Ratios (INRs) for prothrombin time obtained with the CoaguChek Mini and TAS (RapidPointCoag) PT-NC systems are markedly different and also differ from the "true" INR. There is therefore a need for local quality assessment (QA) of the two systems. METHODS: A set of 60 lyophilized artificially depleted and 60 lyophilized coumarin plasmas were tested at 10 centers on both point-of-care testing monitors. Subsets of three and five plasmas were selected as QA plasmas and compared with the remaining 55 to assess the relative ability of the systems to characterize performance at the individual centers. The incidence of aberrant results (outliers; >15% deviation from the true INR) was also recorded. The expected incidence with the QA plasmas was calculated and compared. RESULTS: On both systems, INR with the common sets of 55 lyophilized plasmas varied considerably between centers. With the TAS PT-NC, subsets of five and three European Concerted Action on Anticoagulation (ECAA) artificially depleted plasmas gave good correlation with the 55 plasmas, but the coumarin plasmas performed less well. With the CoaguChek Mini, correlation was good with sets of five artificially depleted QA plasmas and reasonable with three but was less satisfactory with the coumarin plasmas. Outliers were detected with both types of plasmas on both test systems but with variable success. CONCLUSIONS: With the TAS PT-NC, three ECAA artificially depleted lyophilized plasmas provided reliable QA, but five lyophilized coumarin plasmas were required. With the CoaguChek Mini, five artificially depleted plasmas gave reliable QA but coumarin plasmas gave poorer results. ECAA QA plasmas provide a local system for checking INRs obtained with monitors of both types.

Anticoagulants↗
PubMed1994

The reliability of the mean normal prothrombin time of fresh plasmas and of the normal value from a lyophilized 'normal' plasma in prothrombin ratio determination.

The mean normal prothrombin time (MNPT) based on the fresh plasma of 20 healthy individuals is the recommended way to derive a normal value for the prothrombin ratio. This is generally believed to give a reasonable representation of the normal in the local population, but there may be difficulty in obtaining a good representative sample in some centres. The alternative of a uniform lyophilized 'normal' plasma has been suggested. The comparative value of a widely used commercial 'normal' plasma and the MNPT has been assessed in an international study at 37 centres. Two common thromboplastins were tested using the local coagulometer methods. The variability of the results and their relative performance in local thromboplastin calibration to derive the International Sensitivity Index (ISI) were assessed. The reliability of the two types of normal in local system ISI calibration with different lyophilized plasma calibrants has also been tested. When the lyophilized 'normal' was substituted for the MNPT in ISI determination no appreciable difference in the degree of correction for coagulometers effects on International Normalized Ratios was found.

Calibration↗
PubMed1999

Interference of lupus anticoagulants in prothrombin time assays: implications for selection of adequate methods to optimize the management of thrombosis in the antiphospholipid-antibody syndrome.

BACKGROUND AND OBJECTIVE: Prolonged anticoagulation aiming at International Normalized Ratio (INR) values > 3.0 has been recommended for patients with thrombosis and the antiphospholipid-antibody syndrome. We evaluated the influence of anticoagulant antibodies in two different prothrombin time (PT) assays carried out on plasma from lupus anticoagulant patients on oral anticoagulation. DESIGN AND METHODS: INR values obtained with a combined (final test plasma dilution 1:20) and a recombinant (final test plasma dilution 1:3) thromboplastin were compared in 17 patients with persistent lupus anticoagulants (LA) receiving oral anticoagulant treatment and monitored for 69.8 patient-years. Doses of anticoagulant drugs were always assigned based on the results obtained with the combined thromboplastin, aiming at a target INR of 2.5 or 3.0 for patients with venous or arterial thromboembolic disease. Paired determinations with both reagents were also obtained throughout the study period in 150 patients on stable oral anticoagulation but free of antiphospholipid antibodies. Total IgG fractions were purified from selected patients to evaluate effect in the two PT assay systems. RESULTS: No patient experienced recurrence of thrombosis or major bleeding complications (95% confidence interval: 0.1-6.5 per 100 patient-years). INR values with the recombinant reagent were significantly higher than with the combined reagent in 8 LA patients (mean DINR ranging from 0.17 to 0.54) of the degree of anticoagulation was overestimated in all but one LA patients with the recombinant reagent when compared to the DINR observed in non-LA patients (-0.64 +/- 0.42). The anti-cardiolipin IgG titer (r(2) = 0.43, p = 0.004) and the anti-b(2)GPI IgG titer (r(2) = 0.30, p = 0.023) were positively associated with the mean deltaINR observed in LA patients. When added to plasmas with different levels of vitamin K-dependent factors, total IgG fractions from 6 LA patients with significant overestimation of the INR with the recombinant reagent (mean DINR ranging from 0.17 to 0.54, group 1) and from 7 LA patients with mean deltaINR < or = 0.0 (ranging from -0.25 to 0.04, group 2) reproduced the effects observed ex vivo in the two assay systems. However, when total IgG fractions were tested at the same final concentration in the two PT assay systems, there was no difference in the clotting times determined with total IgG fractions from group 1 and group 2 LA patients. Addition of negatively charged liposomes (0.4 and 0.8 mg/mL final concentrations) to platelet free plasma from LA-free patients on stable oral anticoagulation caused a 20% to 48% prolongation of the prothrombin time determined with the recombinant reagent. In contrast, no significant prolongation of the prothrombin time determined with the recombinant reagent was observed upon addition of negatively charged liposomes to plasma from group 1 LA patients. INTERPRETATION AND CONCLUSIONS: These results confirm previous suggestions of assay-dependency of INR values in LA patients on oral anticoagulation. For these patients, accurate INR values may be obtained using combined thromboplastin reagents that permit testing at high plasma dilution.

Adult↗
PubMed1981

[Determination of the prothrombin time and of the activated cephalin time wit semi-automatic Electra 600 apparatus (author's transl)].

This work studies the quality of the response of the Electra 600 for the determination of the prothrombin time (PT) and the activated cephalin time (ACT). The intra-serial precision was good for the PT and the ACT with normal or pathological plasmas (CV 2%). The precision was excellent for the PT (r = 0.98; Electra 600-fibrometer). The correlation coefficient varies between 0.85 and 0.95 for the ACT depending on the nature of the activator chosen. Lactescent plasmas having a protein concentration greater than 85 g/l should be treated manually for measurement of the PT. No interference was noted with other biological substances: eg glucose, bilirubin, hemoglobin. The increasing addition of heparin indicates a correct sensitivity of the response with Electra 600 both for short and long ACT. Autoanalysis renders the determinations of PT and ACT independant of the manipulator, that of the PT being much more rapid than with the manual method

Autoanalysis↗
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↗
PubMed2000

Detailed characterization of an anti-factor IX monoclonal antibody that neutralizes the prolonged ox brain prothrombin time of hemophilia B(M) by synthetic peptides.

In a previous study, we prepared a monoclonal antibody (MoAb) to coagulation factor IX (FIX), designated 65-10, which interfered with the activation of FIX by the activated factor XI/Ca(2+) and neutralized the prolonged ox brain prothrombin time of hemophilia B(M) [11,12]. The location of the epitope on the FIX for 65-10 MoAb is (168) Ile-Thr-Gln-Ser-Thr-Gln-Ser-Phe-Asn-Asp-Phe-Thr-Arg-Val-Val(182) [21]. In this paper, we studied in more detail an epitope on FIX using the systematic substitution of different amino acids at each residue of the epitope peptides and the influence of the epitope peptide on the prolonged ox brain prothrombin time of the hemophilia B(M) plasma of 65-10 MoAb. In the replacement set of amino acids, peptides showing low or no reactivity to 65-10 were (175)Phe --> Asp, Glu, Gly, Lys, Arg, Thr, Val, (176)Asn --> Asp, Glu, Phe, Ile, Lys, Leu, Pro, Val, Tyr, (177)Asp --> Cys, Glu, Phe, Ile, Lys, Leu, Met, Pro, Gln, Arg, Ser, Thr, Val, Trp, Tyr, and (178) Phe --> Pro. These results imply that a hydrophobic molecule of (175) Phe, a hydrophilic molecule of (176)Asn, and a negative charge molecule of (177)Asp were important to the epitope. The 65-10 MoAb antibody neutralized the prolonged ox brain prothrombin time of hemophilia B(M) Nagoya 2 ((180)Arg -->Trp) and Kashihara ((181)Val --> Phe) as well as B(M) Kiryu ((313)Val --> Asp) and Niigata ((390)Ala --> Val). This reaction was inhibited by preincubation with a (168) Ile-Thr-Gln-Ser-Thr-Gln-Ser-Phe-Asn-Asp-Phe-Thr-Arg-Val-Val(182) peptide conjugated with bovine serum albumin (BSA). 65-10 MoAb that has been useful in detailing epitopes will be useful for qualitative analysis of hemophilia B(M).

Amino Acid Sequence↗