Chemistry: analytical and immunological testing – Clotting or clotting factor level tests
Reexamination Certificate
2001-10-10
2004-09-28
Wallenhorst, Maureen M. (Department: 1743)
Chemistry: analytical and immunological testing
Clotting or clotting factor level tests
C422S073000, C600S369000, C705S002000, C709S217000
Reexamination Certificate
active
06797519
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the field of hemostasis, and more particularly, the present invention relates to methods and apparatus for communicating measured characteristics of a blood sample via an electronic network for the purpose of diagnosing hemostasis.
BACKGROUND OF THE INVENTION
The Clinical Hemostasis Handbook, by Laposata et al., defines normal hemostasis as the “controlled activation of clot formation and clot lysis that stops hemorrhage without permitting inappropriate thrombosis.” This means that hemostasis is the net result of two systems working in tandem, the coagulation system—the system that produces the clot, and the fibrinolytic system—the system that dissolves the clot. When the balance between the two systems shifts towards procoagulation, the result is thrombosis. When the balance shifts toward fibrinolysis, the result is hemorrhage. Therefore, a hemostasis test that does not measure the net product of both the coagulation and fibrinolytic systems, such as provided by the TEG® haemostasis analyzer available from Haemoscope Corporation of Niles, Ill., will fail to properly analyze patient hemostasis. For example, in the case of fibrinolysis secondary to hypercoagulability, D-dimer, fibrinogen degradation product (FDP) and fibrinogen split product (FSP) tests would show high fibrinolytic activity, while prothrombin time (PT) and activated partial thromboplastin time (aPTT) results would be normal due to their inherent lack of sensitivity to the hypercoagulable state. Based on these results, antifibrinolytic drugs might be prescribed, shutting off the fibrinolytic system, producing an imbalance toward procoagulability, and could result in acute myocardial infarct, stroke, etc.
Recent advances in the understanding of hemostasis mechanisms have recognized the value of whole-blood monitoring techniques such as provided by the TEG® haemostasis analyzer. As a result, the older view of a separate intrinsic and extrinsic coagulation system has been abandoned along with the waterfall descriptions of coagulation mechanisms with one enzyme working after another and with some mechanisms of feedback amplification and inhibition derived in a plasma milieu. None of this theory was actually applicable in moving blood. These concepts have been replaced by a concept of enzyme complexes existing on the surface of cells, passing one another their substances until the final product, fibrin, is formed. The cell surfaces of importance are those of the platelets, which are activated and adhere to the site of injury. They localize the clotting process, enhance their activities, protect the enzyme complexes from inhibitors that circulate, and protect against propagation of the clotting activation downstream.
The surface concept provides an explanation of how some individuals with only a few percent of plasma coagulation factors can maintain hemostasis, while these same individuals will hemorrhage if their platelet function is compromised. Since prior tests were designed to use substitutes for platelet surfaces, it is readily understood why these tests do not agree with the whole-blood analysis technique, which uses the actual cellular surfaces to monitor hemostasis. Once the importance of the platelet surfaces and of other cellular surfaces and their interactions with the hemostasis process is understood, the value of prior tests comes into question. Since the whole-blood analysis techniques, such as provided by the TEG® haemostasis analyzer, is sensitive to platelet function, plasma factors, activators, and inhibitors of coagulation, it represents an ideal monitor for hemostasis.
The whole-blood analysis technique used by the TEG® haemostasis analyzer allows acquisition of continuous quantitative information on the developing clot; the time it takes for the first fibrin to develop, the kinetics of clot development and the strength and stability of the clot, taking into consideration all of the components that make blood clot or lyse. Ignoring the interactive nature of hemostasis by analyzing separated blood components such as plasma, red blood cells, white blood cells, platelets, fibrinogen level or factor assay can result in artifacts that do not reflect the clinical condition. This should serve as a caution against basing therapy on these analyses alone, especially since there are significant risks associated with blood transfusions. Also, measuring single factors quantitatively can be misleading because the quantity, as measured by an assay, does not reflect the actual functional activity. Functional activity of a factor also depends on the presence and activity of activators, inhibitors, and cellular elements.
The TEG® haemostasis analyzer is an effective point-of-care test of hemostasis that can identify whether a patient has normal hemostasis, and if not, whether the abnormality is due to surgical, coagulopathy, or residual anticoagulation therapy. If the patient has a coagulopathy, the test results provided by the TEG® haemostasis analyzer can be used to identify the specific therapy to treat the condition. For example, the results can be used to determine if the patient needs fresh frozen plasma, cryoprecipitate, platelets, antifibrinolytic drugs, or thrombolytic drugs. In fact, potential therapies can first be applied in vitro to confirm their effect on the patient's blood sample before the patient is treated, and the in vivo effect may be evaluated by subsequent testing of the patient. This has been demonstrated by Kang et al., who found that “[t]he judicious use of a small dose of &egr;-aminocaproic acid, when its efficacy was confirmed in vitro (using results provided by a TEG® haemostasis analyzer), effectively treated the severe fibrinolysis without clinical thrombotic complications. In a prospective study of cardiac surgery, Shore-Lesserson concluded “the use of [whole-blood] analysis (provided by a TEG® haemostasis analyzer) in a transfusion algorithm allowed for identification and appropriate treatment of specific interoperative abnormalities of hemostasis. This intervention resulted in fewer postoperative transfusions and improved hemostasis. [R]esults (provided by a TEG® haemostasis analyzer) are readily available in the operating room thus making it effective as a point-of-care coagulation monitor.”
Thus, the TEG® haemostasis analyzer is a monitoring device, like the EKG, in that it is run to confirm that patient hemostasis is normal, and can assist the physician's differential diagnosis of coagulopathy and guide a selective treatment with blood components and suitable pharmacological therapy. The analysis provided by the TEG® haemostasis analyzer is not intended to replace standard laboratory tests, such as the various separate blood component tests. The TEG® haemostasis analyzer will provide the physician an indication of whether the patient has normal hemostasis. If yes, then the use of laboratory tests will add unnecessary cost and/or provide misleading information. However, when the TEG® haemostasis analyzer shows coagulopathy, the results in conjunction with other laboratory tests assist in differential diagnosis and treatment.
Recently, due to dramatic changes in health care systems worldwide, the reduction of cost has become a prominent factor in the economic survival of the healthcare system. Use of whole-blood monitoring techniques in connection with diagnosis of hemostasis, and particularly the TEG® haemostasis analyzer, can reduce or eliminate the number of laboratory tests ordered for a patient and can be instrumental in reducing blood component transfusions. However, because of the complexity of the process of hemostasis, it is important that the physician fully understand the indications associated with the whole-blood testing results. These issues, however, typically arise during surgery or other invasive procedures such as cardiac catheterization or angioplasty, in trauma situations such as gunshot or knife wounds in the emergency room (ER), in obstetrics, and in int
Cohen Benjamin M.
Cohen Eli
Navickas Irene A.
Robinson Barry N.
Haemoscope Corporation
Wallenhorst Maureen M.
LandOfFree
Method and apparatus for diagnosing hemostasis does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for diagnosing hemostasis, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for diagnosing hemostasis will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3264774