One-stage prothrombin assay and compositions useful therein
AssigneeOrtho Diagnostics, Inc.
InventorsD. Joseph Baughman, Ann Lytwyn
Life of this patent
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Abstract
A one-stage prothrombin assay which measures the exponential rate of thrombin production in thromboplastin-treated, recalcified plasma. A serum reagent reduces the lag time before thrombin production substantially to zero for both normal and abnormal plasma, thus allowing measurements to be made in just a few minutes.
Claims21
A method for determining, for a fibrinogen-normal individual, the effectiveness of that portion of the blood clotting mechanism measured by a conventional one-stage prothrombin time test which comprises the steps of:
- (a) determining the exponential rate of thrombin formation in a mixture comprising effective thrombin-forming concentrations of thromboplastin, calcium ion, and test plasma from said individual;
- and
- (b) comparing this determined rate to a compilation of rates for plasmas of known clotting properties.
A method for determining, for a fibrinogen-normal individual, the effectiveness of that portion of the blood clotting mechanism measured by a conventional one-stage prothrombin time test which comprises the steps of:
- (a) combining effective concentrations of a chromogenic substrate specific for thrombin, thromboplastin, calcium ion, serum reagent, and test plasma from said individual at a controlled temperature, pH, and ionic strength to form a mixture;
- (b) measuring the change with time in absorbance of said mixture at a wavelength effective for detecting the cleaved chromophore of the chromogenic substrate;
- (c) plotting the change with time in absorbance measured in step (b) against time;
- (d) calculating the exponential rate of thrombin formation (a) from the plot in step (c) according to the formula e.sup.at ;
- and
- (e) comparing the calculated rate to a compilation of rates for plasmas of known clotting properties.
A method for determining the one-stage prothrombin time for a fibrinogen-normal individual which comprises the steps of:
- (a) determining the exponential rate of thrombin formation in a mixture comprising effective thrombin-forming concentrations of thromboplastin, calcium ion, and test plasma from said individual;
- and
- (b) calculating the one-stage prothrombin time from said determined rate by use of a standard curve correlating the exponential rate of thrombin formation and the one-stage prothrombin time.
A method for determining the one-stage prothrombin time for a fibrinogen-normal individual which comprises the steps of:
- (a) combining effective concentrations of a chromogenic substrate specific for thrombin, thromboplastin, calcium ion, serum reagent, and test plasma from said individual at a controlled temperature, pH, and ionic strength to form a mixture;
- (b) measuring the change with time in absorbance of said mixture at a wavelength effective for detecting the cleaved chromophore of the chromogenic substrate;
- (c) plotting the change with time in absorbance measured in step (b) above against time;
- (d) calculating the exponential rate of thrombin formation (a) from the plot in step (c) above according to the formula e.sup.at ;
- and
- (e) determining the one-stage prothrombin time for said plasma by comparing the calculated rate obtained in step (d) above to a standard curve relating exponential rate of thrombin formation and one-stage prothrombin time.
A method for determining the exponential rate of thrombin formation for an individual which comprises the steps of:
- (a) combining effective concentrations of a chromogenic substrate specific for thrombin, thromboplastin, calcium ion, serum reagent, and test plasma from said individual at a controlled temperature, pH, and ionic strength to form a mixture;
- (b) measuring the change with time in absorbance of said mixture at a wavelength effective for detecting the cleaved chromophore of the chromogenic substrate;
- (c) plotting the change with time in absorbance measured in step (b) against time;
- and
- (d) calculating the exponential rate of thrombin formation (a) from the plot in step (c) according to the formula e.sup.at.
A method for determining the exponential rate of thrombin formation for an individual in thromboplastin-treated, recalcified plasma which comprises the steps of:
- (a) combining effective concentrations of a chromogenic substrate specific for thrombin, thromboplastin, calcium ion, serum reagent, and test plasma from said individual at a controlled temperature to form a mixture;
- (b) measuring at from one to three specified times the change with time in absorbance of said mixture at a wavelength effective for detecting the cleaved chromophore of the chromogenic substrate;
- and
- (c) estimating the exponential rate of thrombin formation by comparing the change with time in absorbance at each specified time measured in step (b) above to a standard curve relating the change with time in absorbance at each such specified time and the exponential rate of thrombin formation.
A method for determining the exponential rate of thrombin formation for an individual in thromboplastin-treated, recalcified plasma which comprises the steps of:
- (a) combining effective concentrations of a chromogenic substrate specific for thrombin, thromboplastin, calcium ion, serum reagent, and test plasma from said individual at a controlled temperature to form a mixture;
- (b) measuring at from one to three specified times the absorbance of said mixture at a wavelength effective for detecting the cleaved chromophore of the chromogenic substrate;
- and
- (c) estimating the exponential rate of thrombin formation by comparing the absorbance at each specified time measured in step (b) above to a standard curve relating the absorbance at each such specified time and the exponential rate of thrombin formation.
Dependencies are inferred from the claim text.