Chemistry: analytical and immunological testing – Clotting or clotting factor level tests
Reexamination Certificate
1999-08-12
2002-08-06
Wallenhorst, Maureen M. (Department: 1743)
Chemistry: analytical and immunological testing
Clotting or clotting factor level tests
C436S073000, C436S074000, C436S079000, C436S084000, C436S164000, C422S073000, C422S082090, C600S369000, C073S064410, C073S064430
Reexamination Certificate
active
06429017
ABSTRACT:
BACKGROUND OF THE INVENTION
Blood clots are the end product of a complex chain reaction where proteins form an enzyme cascade acting as a biologic amplification system. This system enables relatively few molecules of initiator products to induce sequential activation of a series of inactive proteins, known as factors, culminating in the production of the fibrin clot. Mathematical models of the kinetics of the cascade's pathways have been previously proposed.
Thrombosis and hemostasis testing is the in vitro study of the ability of blood to form clots and to break clots in vivo. Coagulation (hemostasis) assays began as manual methods where clot formation was observed in a test tube either by tilting the tube or removing fibrin strands by a wire loop. The goal was to determine if a patient's blood sample would clot after certain materials were added. It was later determined that the amount of time from initiation of the reaction to the point of clot formation in vitro is related to congenital disorders, acquired disorders, and therapeutic monitoring. In order to remove the inherent variability associated with the subjective endpoint determinations of manual techniques, instrumentation has been developed to measure clot time, based on (1) electromechanical properties, (2) clot elasticity, (3) light scattering, (4) fibrin adhesion, and (5) impedance. For light scattering methods, data is gathered that represents the transmission of light through the specimen as a function of time (an optical time-dependent measurement profile).
Two assays, the PT and APTT, are widely used to screen for abnormalities in the coagulation system, although several other screening assays can be used, e.g. protein C, fibrinogen, protein S and/or thrombin time. If screening assays show an abnormal result, one or several additional tests are needed to isolate the exact source of the abnormality. The PT and APTT assays rely primarily upon measurement of time required for clot time, although some variations of the PT also use the amplitude of the change in optical signal in estimating fibrinogen concentration.
Blood coagulation is affected by administration of drugs, in addition to the vast array of internal factors and proteins that normally influence clot formation. For example, heparin is a widely-used therapeutic drug that is used to prevent thrombosis following surgery or under other conditions, or is used to combat existing thrombosis. The administration of heparin is typically monitored using the APTT assay, which gives a prolonged clot time in the presence of heparin. Clot times for PT assays are affected to a much smaller degree. Since a number of other plasma abnormalities may also cause prolonged APTT results, the ability to discriminate between these effectors from screening assay results may be clinically significant.
The present invention was conceived of and developed for predicting haemostatic dysfunction in a sample based on one or more time-dependent measurement profiles, such as optical time-dependent measurement profiles. In addition, the present invention is directed to predicting the presence of Disseminated Intravascular Coagulation in a patient based on a time-dependent profile, such as an optical transmission profile, from an assay run on the patient's blood or plasma sample.
SUMMARY OF THE INVENTION
The present invention is directed to a method for detecting precipitate in a test sample in the absence of clot formation. The method includes providing a test sample and adding thereto a reagent, the reagent alone or in combination with additional reagents causing the formation of a precipitate. The reagent preferably comprises a metal divalent cation and optionally includes a clot inhibiting substance. The detection of the precipitate can be qualitative or quantitative, and the precipitate can be detected such as by a clotting assay, a latex agglutination or gold sol assay, an immunoassay such as an ELISA, or other suitable method that would allow for detection and/or quantitation of the precipitate. The formation of the precipitate can be detected as an endpoint value, or kinetically. This precipitate detection allows for predicting Haemostatic Dysfunction in patients. The present invention is useful for predicting Haemostatic Dysfunction that can lead to bleeding or thrombosis, or specifically to Disseminated Intravascular Coagulation (DIC).
More particularly, the present invention is directed to a method comprising adding a reagent to a test sample having at least a component of a blood sample from a patient, measuring the formation of a precipitate due to the reaction of the test sample and the reagent, over time so as to derive a time-dependent measurement profile, the reagent capable of forming a precipitate in the test sample without causing substantial fibrin polymerization. The invention is also directed to a method for determining whether or not a patient has haemostatic dysfunction, comprising obtaining a blood sample from a patient, obtaining plasma from said blood sample, adding a reagent capable of inducing the formation of a precipitate in patients with haemostatic dysfunction without causing any substantial fibrin polymerization, taking one or more measurements of a parameter of the sample wherein changes in the sample parameter are capable of correlation to precipitate formation if present, and determining that a patient has haemostatic dysfunction if precipitate formation is detected.
The present invention is also directed to a method for determining in a patient sample the presence of a complex of proteins comprising at least one of a 300 kD protein, serum amyloid A and C-reactive protein, comprising obtaining a test sample from a patient, adding an alcohol, a clot inhibitor, and a metal cation, wherein a precipitate is formed which comprises a complex of proteins including at least one of a 300 kD protein, serum amyloid A and C-reactive protein.
The invention is also directed to a method comprising adding a coagulation reagent to an aliquot of a test sample from a patient, monitoring the formation of fibrin over time in said test sample by measuring a parameter of the test sample which changes over time due to addition of the coagulation reagent, determine a rate of change, if any, of said parameter in a period of time prior to formation of fibrin in said test sample, if the determined rate of change is beyond a predetermined threshold, then with a second aliquot of the patient test sample, add thereto a reagent that induces the formation of a precipitate in the absence of fibrin polymerization, measuring the formation of the precipitate over time, and determining the possibility or probability of haemostatic dysfunction based on the measurement of the precipitate.
The invention is also directed to a method for monitoring an inflammatory condition in a patient, comprising adding a reagent to a patient test sample, the reagent capable of causing precipitate formation in some patient test samples without causing fibrin polymerization, measuring a parameter of the test sample over time which is indicative of said precipitate formation, determining the slope of the changing parameter, repeating he the above steps at a later date or time, wherein an increase or decrease in the slope at the later date or time is indicative of progression or regression, respectively, of the inflammatory condition.
The invention is further directed to a method for diagnosing and treating patients with haemostaic dysfunction, comprising adding a reagent to a test sample that causes precipitate formation without causing fibrin polymerization, taking measurements over time of a parameter of the test sample that changes due to the formation of the precipitate, determining the rate of change of said parameter, determining that a patient has haemostatic dysfunction if said rate of change is beyond a predetermined limit; intervening with treatment for said haemostatic dysfunction if said rate of change is beyond the predetermined limit.
The invention also is directed to a method co
Downey Colin
Fischer Timothy J.
Toh Cheng Hock
bioMerieux
Myers Bigel & Sibley & Sajovec
Wallenhorst Maureen M.
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