Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Chemical analysis
Reexamination Certificate
2000-03-17
2002-08-20
Bui, Bryan (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Chemical analysis
C702S022000, C435S006120, C435S007100
Reexamination Certificate
active
06438498
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a system, method and computer implemented process for conducting a variety of assays. More particularly, the instant invention relates to a system, method and computer implemented process for use in analyzing fluid samples. The invention relates even more particularly to calculating or collecting a sample transformation time or any of a variety of sample information by moving a sample over a sensor, during data collection, to dissolve a reagent or to prevent the accumulation of unwanted material on or about the sensor surface.
BACKGROUND OF THE INVENTION
Numerous procedures and techniques exist for analyzing and testing blood and other body fluids. To name one, coagulation techniques may be used to collect a wide variety of information from given samples of blood. While some of these procedures are relatively simple, others can be more sophisticated and require multiple steps or preparations. For instance, many procedures involving blood samples require the addition of reagents to commence the formation of clots or other steps to prepare the sample for data collection and to account for the unique characteristics of blood.
For example, keeping blood in a fluid state, termed hemostasis, requires a subtle balance of pro- and anticoagulants. In the human body, procoagulants prevent excessive bleeding by blocking blood flow from a damaged vessel, whereas anticoagulants prevent clots from forming in the circulating system which could otherwise block blood vessels and lead to myocardial infarction or stroke.
The biochemical sequence leading to a blood clot is termed the coagulation cascade. This mechanism is based on catalytic conversion of fibrinogen, a soluble plasma protein, to insoluble fibrin. The enzyme catalyzing this reaction is thrombin. which does not permanently circulate in the blood in an active form but exists as prothrombin, the inactive precursor of thrombin. Conversion to thrombin occurs in the presence of calcium ions and tissue thromboplastin. This mechanism is known as the extrinsic pathway. A second, more complex, intrinsic pathway is activated by clotting factors associated with platelets.
Diagnosis of hemorrhagic conditions such as hemophilia, where one or more of the twelve blood clotting factors may be defective, can be achieved by a wide variety of coagulation tests. In addition, several tests have been developed to monitor the progress of thrombolytic therapy. Other tests have been developed to signal a prethrombolytic or hypercoagulable state, or to monitor the effect of administering protamine to patients during cardiopulmonary bypass surgery. However, the main value of coagulation tests is in monitoring oral and intravenous anticoagulation therapy. Three of the key diagnostic tests are activated partial thromboplastin time (APTT), prothrombin time (PT), and activated clotting time (ACT).
An APTT test evaluates the intrinsic and common pathways of coagulation. For this reason APTT is often used to monitor intravenous heparin anticoagulation therapy. Specifically, it measures the time for a fibrin clot to form after the activating agent, calcium, and a phospholipid have been added to the citrated blood sample. Heparin administration has the effect of suppressing clot formation.
A PT test evaluates the extrinsic and common pathways of coagulation and, therefore, is used to monitor oral anticoagulation therapy. The oral anticoagulant coumadin suppresses the formation of prothrombin. Consequently, this test is based on the addition of calcium and tissue thromboplastin to the blood sample.
An ACT test evaluates the intrinsic and common pathways of coagulation. It is often used to monitor anticoagulation via heparin therapy. The ACT test is based on addition of an activator to the intrinsic pathway to fresh whole blood to which no exogenous anticoagulant has been added.
The standard laboratory technology for coagulation tests typically uses a turbidimetric method. For analysis, whole-blood samples are collected into a citrate vacutainer and then centrifuged. The assay is performed with plasma to which a sufficient excess of calcium has been added to neutralize the effect of citrate. For a PT test, tissue thromboplastin is provided as a dry reagent that is reconstituted before use. This reagent is thermally sensitive and is maintained at 4 degrees C. Aliquots of sample and reagent are transferred to a cuvette heated at 37 degrees C, and the measurement is made based on a change in optical density.
As an alternative to the turbidimetric method, Beker et al. (See, Haemostasis (1982) 12:73) introduced a chromogenic PT reagent (Thromboquant PT). The assay is based on the hydrolysis of p-nitroaniline from a modified peptide, Tos-Gly-Pro-Arg-pNA, by thrombin and is monitored spectrophotometrically.
Coagulation monitors are known for the analysis of whole blood. For example, a unit-use cartridge has been described in U.S. Pat. No. 4,756,884 in which dry reagents are placed into the analyzer which is then heated to 37 degrees C before a drop of blood is introduced. The sample is mixed with the reagent by capillary draw. The detection mechanism is based on laser light passing through the sample. Blood cells moving along the flow path yield a speckled pattern specific to unclotted blood. When the blood clots, movement ceases producing a pattern specific to clotted blood.
An automatic coagulation timer has been described which measures the activated clotting time (ACT) in blood samples from patients during cardiopulmonary bypass. The sample is added to a cartridge which incorporates a stirring device onto which the clot forms. Motion of the stirring device is controlled by a photo optical detector (See, Keeth et al., Proceedings Am. Acad. Cardiovascular Perfusion (1988) 9:22).
U.S. Pat. No. 4,304,853 discloses the use of a substrate which produces an electroactive product on reaction with the enzyme thrombin. A sensor is used to detect the electroactive product. The disclosure does not include a single-use cartridge and does not disclose the use of a second sensor to monitor the location of the sample.
U.S. Pat. No. 4,497,744 discloses a turbidometric method for assaying coagulation. Plasma containing an excess of citrate is used in the test. A reagent which induces clotting is added, the sample is placed in a turbidometer, and coagulation is indicated by an increase in the turbidity of the sample.
U.S. Pat. No. 5,096,669, incorporated herein by reference, includes the general format for use of a cartridge and analytzer for blood chemistry testing such as potassium and glucose blood levels and the use of a pump to move a sample fluid to a sensor region in a single direction.
U.S. Pat. No. 5,200,051, incorporated herein by reference, discloses efficient methods of microfabrication of sensor devices for analysis of analytes.
U.S. Pat. No. 5,302,348 discloses a blood coagulation test apparatus in which blood is forced to traverse a capillary conduit. When the time for traverse exceeds the previous time by a certain percentage, coagulation is deemed to have occurred. The apparatus includes an unclosed entry port which is connected to two conduits, the first receiving the sample to be assayed, the second receiving overflow sample.
U.S. Pat. Nos. 5,447,440 and 5,628,961, both incorporated herein by reference, disclose a single-use cartridge and reader used in coagulation assays. The condition of the sample is determined by its flow properties as detected, for example, by a conductivity sensor.
U.S. Pat. No. 5,526,111 discloses a method for calculating a coagulation characteristic of a sample of blood, a blood fraction, or a control. This method uses a backwards looking approach to determine a slope of an envelope at each of a number of stored envelope values from which the coagulation characteristic is determined. However, this method uses a fixed or predetermined sampling time and rectifies stored sample values to provide its envelope values. In addition, this method requires storing the envelope values as well as the sa
Lauks Imants R.
Maczuszenko Andy
Opalsky Cindra A. Widrig
Opalsky David
Bui Bryan
I-Stat Corporation
Katten Muchin Zavis & Rosenman
Villacorta Gilberto M.
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