Chemistry: analytical and immunological testing – Optical result
Reexamination Certificate
2000-11-28
2004-03-16
Warden, Jill (Department: 1743)
Chemistry: analytical and immunological testing
Optical result
C436S043000, C436S045000, C436S047000, C436S054000, C436S171000, C436S069000, C422S072000
Reexamination Certificate
active
06706536
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the field of devices useful for containing and analyzing blood for carrying out coagulation studies and other chemistry procedures, and a method for carrying out the procedures, including monitoring oral anticoagulant therapy to take into account the platelet count in determining prothrombin times (PT), International Normalized Ratios (INR), and partial thromboplastin times (PT).
2. Description of the Prior Art
Handling of human blood and body fluids in open containers carries with it the potential danger of the transmission of HIV (AIDS), Hepatitis B, Hepatitis C and other blood-borne diseases. It is desirable to avoid all human contact with blood. Existing coagulation and chemistry systems have capped holders for the blood which commonly comprise a stoppered tube containing a vacuum therein. One such example of a vacuum tube is the VACUTAINER® (Becton Dickinson). A needle apparatus is used in connection with the container to aspirate a fixed, known quantity of blood or blood plasma by piercing the container cap. The quantity of blood or plasma is then dispensed into open cuvettes where reactions take place. Automatic methods exist to dispose of the spent reactant cuvettes, but the cuvettes, too, are open. This open system has the potential for exposing blood to medical personnel.
In carrying out analyses of human blood, there exist certain inherent risks to those individuals, in particular, medical personnel, who handle the blood containers. The blood borne diseases, if not contained, can be deleterious to the health of those coming into contact with the blood. Blood is generally sampled from humans using a syringe and needle. The needle is inserted into a blood vessel or a catheter through which blood is withdrawn. It is the common practice to withdraw the blood through the needle and deliver the blood from the needle into a sample tube in which the blood can be temporarily stored for transport to the lab.
It is a common practice for a lab technician to remove blood from a sample tube, such as a cuvette, and then perform the appropriate analyses on the blood sample. Often, the testing involves mixing the blood with reagents, and undertaking studies of transformation of blood components, and production of components from enzymes. When the blood tube is opened, or when blood is removed from the tube, there is a risk of spilling the blood, or a risk of human contact with the blood. While medical personnel attempt to guard against these risks by wearing protective gear, such as gloves, face shields, lab coats, and other coverings, the risk of spillage remains. Furthermore, in some cases, due to the cumbersome coverings, gloves, lab coats, shields, and the like, carrying out testing is impeded, and sometimes, the protective coverings worn by individuals must be removed, and then replaced.
While robotics have been employed to facilitate processing of a blood sample. It is known to withdraw blood into a sample container or vial and store the container with one or more other samples, for processing, where a robotic arm is used to withdraw an amount of fluid from the sample vial and transfer that amount to a second vial for further processing. In some cases, the sample contents are transferred from a second vial to yet a third vial for spectrophotometic analysis. The original fluid sample is therefore removed from a container and the risks of handling and spillage, even though done with a robotic apparatus, still have the potential to contaminate the environment outside of the original sample vial.
Similarly, disposal of open containers presents a further problem. Risks of human contact with blood and other body fluids are present during the disposal, since the open container holding the blood sample must be handled, or the blood or fluid sample which has been removed from a closed tube disposed of properly.
A need exists for an apparatus and device which reduces the risk of contacting blood, but at the same time permits test analyses to be carried out. The present invention provides a novel apparatus and method for containing blood at the point of its withdrawal from a source, and up to and throughout its testing, then disposal.
Testing of blood and other body fluids is commonly done in hospitals, labs, clinics and other medical facilities. For example, to prevent excessive bleeding or deleterious blood clots, a patient may receive oral anticoagulant therapy before, during and after surgery. To assure that the oral anticoagulant therapy is properly administered, strict monitoring is accomplished and is more fully described in various medical technical literature, such as the articles entitled “PTs, PR, ISIs and INRs: A Primer on Prothrombin Time Reporting Parts I and II” respectively published November, 1993 and December, 1993 issues of
Clinical Hemostasis Review
, and herein incorporated by reference.
These technical articles disclose anticoagulant therapy monitoring that takes into account three parameters which are: International Normalized Ratio (INR), International Sensitivity Index (ISI) and prothrombin time (PT), reported in seconds. The prothrombin time (PT) indicates the level of prothrombin and blood factors V, VII, and X in a plasma sample and is a measure of the coagulation response of a patient. The INR and ISI parameters are needed so as to take into account various differences in instrumentation, methodologies and in thromboplastins' (Tps) sensitivities used in anticoagulant therapy. In general, thromboplastins (Tps) used in North America are derived from rabbit brain, those previously used in Great Britain from human brain, and those used in Europe from either rabbit brain or bovine brain. The INR and ISI parameters take into account all of these various different factors, such as the differences in thromboplastins (Tps), to provide a standardized system for monitoring oral anticoagulant therapy to reduce serious problems related to prior, during and after surgery, such as excessive bleeding or the formation of blood clots.
As reported in Part I (Calibration of Thromboplastin Reagents and Principles of Prothrombin Time Report) of the above technical article of the
Clinical Hemostasis Review
, the determination of the INR and ISI parameters are quite involved, and as reported in Part II (Limitation of INR Reporting) of the above technical article of the
Clinical Hemostasis Review
, the error yielded by the INR and ISI parameters is quite high, such as about 13%. The complexity of the interrelationship between the International Normalized Ratio (INR), the International Sensitivity Index (ISI) and the patient's prothrombin time (PT) may be given by the below expression (1), wherein the quantity
[
Patient
'
s
PT
Mean
of
PT
Normal
Range
]
is commonly referred to as prothrombin ratio (PR):
INR
=
[
Patient
'
s
PT
Mean
of
PT
Normal
Range
]
ISI
(
1
)
The possible error involved with the use of International Normalized Ratio (INR) is also discussed in the technical article entitled “Reliability and Clinical Impact of the Normalization of the Prothrombin Times in Oral Anticoagulant Control” of E. A. Loeliger et al, published in
Thrombosis and Hemostasis
1985; 53: 148-154, and herein incorporated by reference. As can be seen in expression (1), ISI is an exponent of INR which leads to the possible error involved in the use of INR to be about ±13.5% or possibly even more. A procedure related to the calibration of the ISI is described in a technical article entitled “Failure of the International Normalized Ratio to Generate Consistent Results within a. Local Medical Community” of V. L. Ng et al, published in Am. J. Clin Pathol 1993; 99: 689-694, and herein incorporated by reference.
The unwanted INR deviations are further discussed in the technical article entitled “Minimum Lyophilized Plasma Requirem
Carroll Wallace E.
Jackson R. David
Earley John F. A.
Earley III John F. A.
Harding Earley Follmer & Frailey
Siefke Sam P.
WADA, Inc.
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