Optics: measuring and testing – Blood analysis
Reexamination Certificate
1997-09-18
2001-04-24
Font, Frank G. (Department: 2877)
Optics: measuring and testing
Blood analysis
C356S317000, C356S318000, C422S082090
Reexamination Certificate
active
06222619
ABSTRACT:
TECHNICAL FIELD
The invention generally relates to diagnostic devices and, more particularly, to a point-of-care diagnostic device useful in the quick differential diagnosis of a myocardial infarction or similar event in a subject.
BACKGROUND
Various cardiac markers are used in the diagnosis of cardiac function and disease. Among these markers is troponin. Troponin is a protein complex which regulates the contraction of striated muscle. The troponin protein complex includes three distinct proteins. The first is troponin I which is an inhibitory sub-unit. The second is troponin C which is a calcium binding sub-unit. The third is troponin T, a sub-unit which attaches the troponin protein complex to tropomyosin on the thin filament of the striated muscle.
Troponin I is believed to exist in three isoforms, one of which exists in cardiac muscle, while the other two exist in skeletal muscle. The skeletal muscle isoforms are nearly identical, and have molecular weights of about 19,800 Daltons. Structurally, the cardiac isoform of troponin I is about 60% similar to the skeletal isoforms, and has a molecular weight of about 22,500 Daltons.
After the onset of an acute myocardial infarction, the cardiac isoform of troponin I is measurable in the serum after four to six hours. Peak serum concentrations are reached after twelve to eighteen hours after the acute myocardial infarction. Unlike other cardiac markers (e.g., CK-MB and myoglobin), troponin I levels may remain elevated in the serum for several days before returning to normal. Because of these characteristics, the cardiac isoform of troponin I is used in the diagnosis of acute myocardial infarction.
For example, the OPUS Troponin I from Behring Diagnostics, Inc. of Westwood, Mass. is a fluorogenic enzyme-linked immunoassay (“ELISA” or “EIA”) for the quantitative measurement of troponin I in serum and heparinized plasma. This assay uses two goat polyclonal antibodies that are purified to recognize different polypeptide segments believed to be unique to the cardiac isoform of troponin I.
As detailed in U.S. Pat. No. 5,604,105, issued Feb. 18, 1997 to Jackowski (“the Jackowski patent”), speed is of the utmost importance in obtaining a reliable diagnosis of an acute myocardial infarction. The choice and efficacy of treatment depends to some extent on obtaining a reliable diagnosis of a myocardial infarction versus some other disease state, such as dyspnea.
In the Jackowski patent, a method and device for diagnosing and distinguishing chest pain is described which reportedly can aid an emergency room physician in determining whether or not a patient is presenting with an ischemic event (e.g., a myocardial infarction or unstable angina). The diagnostic test of the Jackowski patent involves the simultaneous detection of three different cardiac markers in a sandwich assay and provides results to the physician within about one-half hour.
However, time is of the essence with an ischemic event where timely treatment can make the difference between life and death. The present generation of clinical diagnostics assays for cardiac markers, such as CK-MB, myoglobin and Troponin I, typically take on the order of 1 hour to perform. Thus, the time delay of the present generation of clinical diagnostics assays, including the one-half hour delay disclosed in the Jackowski patent, to determine the presence of an ischemic event is unacceptable.
Therefore, it would be a significant improvement in the art if means were available to diagnose such an ischemic event in even a shorter time, e.g., something on the order of two minutes.
DISCLOSURE OF INVENTION
Surprisingly, it has been found that by carefully constructing, selecting, and using a biosensor with a three (or more) cardiac marker system, results can be quickly obtained and reported back to the monitoring physician within, for example, two minutes.
The invention thus includes a method of diagnosing a cardiac disease state in as little as two minutes involving the utilization of an evanescent wave assay system in conjunction with a data acquisition and analysis procedure that monitors the precision of assay results in real time (i.e., while data is being acquired).
For ischemic events, such as an acute myocardial infarction, it has been found that reliable results can be obtained within about 1 to 2 minutes for positive specimens. These results are obtainable because patients suffering from acute myocardial infarctions have elevated levels of the cardiac marker proteins in their blood. For such elevated levels, it takes less reaction time to achieve a given precision in the assay determination.
The invention also includes a method of diagnosing a disease state using a diagnostic procedure (e.g., an immunoassay) wherein the testing device informs the person conducting the test of the results of the test as soon as reliable test data is obtained (generally, <5% variation in the reaction rate of the assay). After which point, the diagnostic procedure may be terminated.
The invention thus also includes diagnostic devices, such as biosensors, which utilize the methods of the invention, and methods of making and using such diagnostic devices.
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pate
Christensen Douglas A.
Durtschi Jacob D.
Herron James N.
Britt Trask
Font Frank G.
Merlino Amanda
University of Utah Research Foundation
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