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At least 19 recordsLinked to original sources
PubMed1999

[Suggestions and propositions to resolve some issues for standardization of prothrombin time and activated partial thromboplastin time].

Prothrombin time (PT) and activated partial thromboplastin time (APTT), popularized as a routine assay for screening blood coagulation disorders and monitoring anticoagulant therapy, still involve some issues regarding standardization. In this lecture, we present propositions to resolve these problems in respective laboratory. Although international normalized ratio (INR) calculated by international sensitivity index (ISI) of PT reagent seems to improve discrepancy of sensitivity between reagents, local calibration of sensitivity of PT reagent in respective laboratories (local SI) is reasonable to make INR/ISI system more useful. However, local calibration of reagent is not easy by WHO recommended method in a small size laboratory. By using AK calibrant (IMMUNO AG), one of calibration plasma for INR, we investigated its possibility to calibrate local SI in four different reagents, compared with the recommended methodology. The results led the following process to determine reagent and calibrate local SI for practical use of INR/ISI system. (a) Use PT reagent of which ISI is close to 1.0 if possible, and utilize manufacture's ISI as is for INR. (b) Select PT reagent labeled specific ISI for an instrument as the same as used in the lab., and use the manufacture's ISI as is, if impossible to choose small ISI reagent. (c) If use a reagent of which ISI is close to 2.0 and shown no specific ISI for used detector, adjustment of local SI by commercial calibration plasma is recommended when unavailable warfarinized patient plasma. In APTT, we attempted to evaluate sensitivity between five different APTT reagents with a patient model by hemophilia A plasma contained various FVIII: C. This model reflected difference of sensitivity between reagents in results. Because standardization of APTT is not improved in this point, certification of APTT pattern in each laboratories with patient models is required for not only monitoring of heparinization, but also screening of typical coagulation disorders such as hemophilia and von Willebrand disease.

Humans↗
PubMed1992

Evaluation of prothrombin time and partial thromboplastin time.

Prothrombin time (PT) and partial thromboplastin time (PTT) tests are commonly ordered for hospitalized patients. A significant reduction in laboratory workload and expense can be achieved if these tests are ordered appropriately. The likelihood that the patient will benefit from these tests is small.

American Medical Association↗
PubMedDate not supplied

Influence of fibrinogen degradation products on thrombin time, activated partial thromboplastin time and prothrombin time of canine plasma.

To investigate how thrombin time, activated partial thromboplastin time (APTT) and prothrombin time are influenced by fibrinogen degradation products (FDP), different concentrations (0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8 and 1.0 mg/ml) of the purified FDP X, Y, D and E were added to the plasma of healthy dogs. If fragment Y was added to the plasma a considerable inhibitory effect could be demonstrated for all three test systems. A significant prolongation (p < 0.05) was found for concentrations of > or =0.1 mg/ml (thrombin time, APTT) and > or =0.2 mg/ml (prothrombin time). With FDP Y concentrations from >0.185 mg/ml (prothrombin time) to >0.24 mg/ml (APTT) coagulation time was prolonged beyond the respective reference range. As regards the other fragments, a comparable inhibitory effect could only be shown for fragment X added to the thrombin time test system. This effect can most probably be explained by the competition of the FDP X and fibrinogen for the fibrinogen binding sites of thrombin, rather than by a fibrin polymerization disorder. The results demonstrate that for plasma with normal fibrinogen concentration the group tests are only prolonged beyond the reference range at FDP concentrations very rarely found in spontaneous hyperfibrinolysis.

Animals↗
PubMed1985

Comparison of a chromogenic prothrombin time with clotting prothrombin time in the assessment of clinical coagulation deficiencies.

A chromogenic prothrombin time (CPT) has been compared with the standard prothrombin time (PT) or activated partial thromboplastin time (aPTT) in evaluating the hemostatic abnormality in patients with specific clotting factor deficiencies or liver disease and in patients receiving anticoagulant or fibrinolytic therapy. As expected, the CPT was sensitive to deficiencies of Factors II, V, X, and VII but was unaffected by deficiencies of Factors XII, XI, IX, or VIII. Due to the presence of polybrene in the thromboplastin formulation, the CPT was insensitive to heparin concentrations below 1 unit/mL. However, the assay result prolonged progressively between 1 and 10 units of heparin/mL, indicating that the CPT can be used to assay heparin concentrations within this range. Among patients with liver disease or who were receiving warfarin or fibrinolytic therapy, there was good correlation between the prolongation of the PT and the CPT. The results demonstrate that the CPT was sensitive to the commonly encountered clinical abnormalities in which the PT is prolonged and could be applied for monitoring oral anti-coagulant therapy. However, prolongation of the PT to a given value in different clinical conditions was associated with different degrees of prolongation of the CPT. This differential effect may reflect an abnormality in fibrinogen conversion to fibrin, which prolongs the PT but not the CPT and may also be contributed to by the differential sensitivity of the PT and CPT to specific factor deficiencies. The simplicity and reproducibility of the CPT warrant its further assessment, but correlation with the PT in a variety of clinical conditions is needed before clinical application can be undertaken.

Anticoagulants↗
PubMed1991

The influence of time, temperature and packed cell on activated partial thromboplastin time and prothrombin time.

Activated partial thromboplastin time (APTT) and prothrombin time (PT) were performed in four groups of studies in order to evaluate the influences of time, temperature, and different forms of plasma storage to the result. Different designs for storage of the plasmas were studied, including the plasmas stored either with or without packed cells, the plasmas stored in the cuvette with exact volume for performing the test or in the test tube. The temperatures for store of the plasma were at room temperature, at 4 degrees C and at -70 degrees C. The time for store of the plasma was from 1 hour up to 7 hours. The plasmas included normal pooled plasmas and diseased plasmas. From this study, it is found that the PT test was not easily affected by the temperature, storage time and the form of storage in comparison with the APTT test which was much easily affected by the above conditions. APTT should be done within 2 hours after sampling and the plasma should be stored with the packed cells at 4 degrees C in order to obtain a reliable result. PT could be done within 7 hours without influence to the result if the plasma was stored with the packed cells at 4 degrees C. No significant cold-induced shortening of PT could be noted when the plasma was incubated at 4 degrees C up to 7 hours. In either PT or APTT, the most suitable condition for storing the plasma should be with the packed cells at 4 degrees C.

Blood Preservation↗
PubMed1997

Properties of optical data from activated partial thromboplastin time and prothrombin time assays.

Changes in characteristics of optical transmittance data from coagulation assays were examined as a function of concentration of coagulation proteins or anticoagulants. Transmittance data were collected for activated partial thromboplastin time (APTT) and prothrombin time (PT) assays from: 1) plasmas prepared by mixing normal plasmas with deficient plasmas to give varying levels of coagulation proteins; 2) plasmas containing added heparin; and 3) 200 specimen plasmas that were also assayed for fibrinogen, coagulation factors, and other components. Optical profiles were characterized using a set of parameters describing onset and completion of coagulation, magnitude of signal change, rate of coagulation and other properties. Results indicated that parameters other than those typically reported for APTT and PT are associated with individual deficiencies, but that diagnosis of specimen status on the basis of optical data is complex. These results suggest possibilities for expanded interpretation of PT/APTT optical data for clinical or research applications.

Antithrombin III↗
PubMed1994

Intraoperative measurement of activated partial thromboplastin time and prothrombin time with a new compact monitor.

A prospective study was conducted to evaluate a new compact portable coagulation monitor (Ciba-Corning Biotrack 512 Monitor), which enables the clinician to perform instantaneous activated partial thromboplastin time (APTT) and prothrombin time (PT). 126 patients scheduled for heparinized and nonheparinized vascular surgery, and gynaecological surgery, were included. A drop of capillary or venous whole blood was applied in disposable cartridges to successively perform APTT and PT, and the results of the tests were compared with conventional laboratory methods, performed in two different laboratories (Lab. A and B). Comparisons between Lab. A. and Lab. B. enables determination of the bias, precision, and percent of outliers (patients whose values differed more than 20%) in conventional methods. The reference value was defined as the mean of Lab. A. and Lab. B. values. For PT, there were no statistical differences between the capillary and venous samples performed with the portable monitor, and the reference value, for the bias, the precision and the proportion of outliers. For APTT, there were no statistical differences between the capillary and venous samples performed with the portable monitor, and the reference value, for the bias and the precision. The percent of outliers, however, was significantly greater with the venous sample of the compact monitor than with the reference (48 versus 22%), and even if it did not reach the statistical significance (P = 0.07) it was also higher with the capillary sample performed with the Ciba Monitor than with the reference (33%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Diagnostic uses of the activated partial thromboplastin time and prothrombin time.

The activated partial thromboplastin time (APTT) and prothrombin time (PT) have three principal uses. In screening for coagulation disorders (or increased risk of postoperative hemorrhage), the tests add no information to the preoperative care of patients without clinical findings indicative of increased bleeding risk. Furthermore, the prevalence of asymptomatic congenital coagulopathies is so low that false-positive test results greatly outnumber true-positive results. Thus, clinicians may use clinical assessment to screen and should reserve coagulation tests to investigate patients with abnormal findings. In evaluating abnormal bleeding, these tests are sufficiently sensitive that if both are negative, further investigation of the coagulation system is obviated. If one or both tests are positive, the pattern of results directs further attention to limited segments of the coagulation sequence. In monitoring anticoagulation therapy, the APTT and PT tests appear to contribute to the safety and effectiveness of heparin and warfarin therapies, respectively.

Anticoagulants↗
PubMed1995

Determination of normal versus abnormal activated partial thromboplastin time and prothrombin time after cardiopulmonary bypass.

OBJECTIVE: The study's objective was to determine the prothrombin time (PT) and activated partial thromboplastin time (aPTT) values that differentiated normal from excessively bleeding patients immediately after cardiopulmonary bypass (CPB). DESIGN: A prospective blinded study. SETTING: A large academic medical center. PARTICIPANTS: 148 patients were studied. INTERVENTIONS: aPTT and PT were determined by the hospital laboratory and the Biotrack 512 Coagulation Monitor (Ciba Corning Diagnostics, Medfield, MA) from an arterial whole blood sample obtained 10 minutes after protamine administration. Patients were subjectively and objectively defined as "bleeders" or "nonbleeders" with blinded observers. MEASUREMENTS AND MAIN RESULTS: The specificity and sensitivity were determined by a receiver operating characteristic (ROC) analysis. Twenty-three of 148 patients (14.9%) were characterized as bleeders. The laboratory PT had a maximal specificity and sensitivity of 78% and 75%, respectively, at a value of 15.4 s, with a negative and positive predictive value of 93% and 33%, respectively. The maximal specificity and sensitivity of the laboratory aPTT was 64% and 76%, respectively, at a value of 46 s, with a negative and positive predictive value of 89% and 33%, respectively. aPTT and PT approached normal values after 12 hours in the intensive care unit. CONCLUSION: The aPTT and PT values that produce the maximal sensitivity and specificity in the ROC analysis may be helpful to differentiate patients who are bleeding excessively from those patients who are not after CPB and to guide transfusion of blood products. New whole blood coagulation devices with rapid turn-around times had similar predictive value for bleeding tendency compared with standardized laboratory tests.

Adult↗
PubMed1993

Intraoperative measurement of activated partial thromboplastin time and prothrombin time by a portable laser photometer in patients following cardiopulmonary bypass.

Intraoperative capabilities to rapidly assess coagulation status following cardiopulmonary bypass (CPB) may be of benefit in providing optimal hemostasis and transfusion management, because CPB causes abnormalities in coagulation that may increase morbidity and mortality. The Ciba Corning 512 coagulation monitor (Ciba Corning, Medfield, MA) is a compact and portable device that rapidly determines the prothrombin time (PT) and activated partial thromboplastin time (APTT) in whole blood samples. One hundred patients requiring CPB had APTT and PT determined in whole blood specimens by the 512 coagulation monitor and in plasma specimens by the hospital laboratory from the same arterial blood sample obtained after protamine administration. Correlation coefficients of 0.95 and 0.77 were obtained for the paired APTT and PT tests, respectively (P < 0.01). A bias of 12.6 seconds and 0.77 seconds was determined for the APTT and PT, respectively. The 95% confidence intervals of the bias of the APTT and PT were 9.7 seconds to 15.5 seconds and 0.3 seconds to 1.16 seconds, respectively. The 512 coagulation monitor provided APTT and PT results in less than 3 minutes compared to approximately 45 minutes for the hospital laboratory. A reduction in accuracy was associated with the 512 coagulation monitor PT and APTT when different sampling sites were used. The 512 coagulation monitor accuracy was not affected by a variation of hemoglobin concentration or platelet count between 6 and 12 gm/dL and 15 to 300 x 10(9)/L, respectively. In conclusion, the 512 coagulation monitor provided a rapid APTT and PT result, but the APTT was less accurate. Speeding access to hospital laboratory results would be even more efficacious and accurate.

Adult↗
PubMed1987

New modified activated partial thromboplastin time and prothrombin time methods using a synthetic chromogenic substrate in combination with diazotization.

A chromogenic substrate, H-D-Phe-Pip-Arg-pNA (S-2238) is a highly specific substrate to thrombin and releases p-nitroaniline (pNA) by the action of thrombin. We describe new modified APTT and PT methods using S-2238 in combination with the diazotization of pNA. In the modified APTT method, 100 microliter citrated plasma (diluted to 10-fold), 90 microliter 1 mM S-2238, 100 microliter 20 mM CaCl2 and 100 microliter Actin were mixed in an ice-bath, then incubated for 8 min at 37 degrees C. The reaction was stopped, and the generated pNA was diazotized by adding the following solutions sequentially: 975 microliter 0.04% sodium nitrite, 975 microliter 0.3% ammonium sulfamate and 975 microliter 0.07% N-(l-naphthyl)-ethylenediamine dihydrochloride. Diazotization changed pNA from yellow to pink. Then, absorbance at 545 nm was read, and values were expressed as thrombin units/ml plasma. In the modified PT method, 100 microliter citrated plasma (diluted to 20-fold), 90 microliter 1 mM S-2238 and 200 microliter tissue thromboplastin-C solution were mixed and processed as above. Correlations of the present modified APTT and APTT methods, and of modified PT and PT methods were significant (r = 0.426, p less than 0.01 and r = 0.561, p less than 0.01, respectively).

Aniline Compounds↗