Chemical apparatus and process disinfecting – deodorizing – preser – Analyzer – structured indicator – or manipulative laboratory... – Means for analyzing liquid or solid sample
Reexamination Certificate
2001-06-29
2004-09-07
Alexander, Lyle A. (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Analyzer, structured indicator, or manipulative laboratory...
Means for analyzing liquid or solid sample
C422S051000, C422S067000, C422S068100, C436S164000
Reexamination Certificate
active
06787109
ABSTRACT:
The invention relates to a test element analysis system for the analytical investigation of a sample, in particular a body fluid, of human beings or of animals. The system comprises two components, namely test elements, which are, in order to perform an analysis, brought in contact to a sample to be investigated, and in which a measurable change which is characteristic of the analysis takes place in a measurement zone, as well as an evaluation apparatus comprising a positioning unit for positioning a test element in a measuring position, a measuring unit for measuring the characteristic change, and an electronic evaluation device for obtaining a result of the analysis, based on the result of the measurement.
Test element analysis systems are common in medical science, in particular for the analysis of blood and urine. In most cases, the test elements have the form of test strips. Other forms of test elements are, however, also common, e.g. flat, essentially square plates.
Generally the test elements contain reagents the reaction of which with the sample leads to a detectable change of the test element; this change is measured with the evaluation apparatus belonging to the system. Very common are photometric analysis systems, in which the reaction causes a color change in a detection layer of the test element. The color change is then measured photometrically. Electrochemical analysis systems are also of important significance. In these, an electrically measurable change of the test element occurs due to the reaction. Apart from these analysis systems working with reagents, reagent-free analysis systems are discussed, too. In these, an analytically characteristic property (e.g. the light absorption spectrum) of the sample itself is measured after contacting the test element with the sample. The invention is generally suitable in combination with all these procedures.
Test element analysis systems are used in medical laboratories. The invention is, however, particularly intended for applications in which the patients themselves perform the analysis in order to monitor their health state (home monitoring). This is of particular medical importance for diabetics, who have to check the glucose concentration in their blood several times a day in order to adjust the insulin injections. For such applications, the evaluation apparatuses must be lightweight, small, battery-operated, inexpensive and robust.
A fundamental problem is due to the fact that the measured quantity which is characteristic for the analysis, is in many cases very temperature-dependent. This temperature dependence is, in many cases, about one or two percent per degree. In home-monitoring, the exposure of the analysis system to high temperature changes is unavoidable. Temperature variations of at least ±5° have to be taken into account. Much higher temperature variations may occur, if measurements are to be performed under unusual conditions (e.g. in a car or outdoors).
In order to avoid the measurement uncertainties resulting from this, it was proposed to control the temperature of the measuring zone of the test element to a constant value by means of a corresponding constant-temperature unit. For example, U.S. Pat. No. 5,035,862 describes temperature control of individual test fields of urine test strips by means of inductive heating. However, such procedures are, due to their high energy consumption, not practicable for small battery-operated apparatuses.
Some analysis systems use a temperature measurement in order to allow a correction of measurement errors caused by temperature variations. This is commonly achieved by an electrical temperature sensor (e.g. a thermocouple or a thermal resistor). Due to design limitations of commonly used analysis systems, the temperature sensor is located at a place remote from the measuring zone of the test element. It is, therefore thermally separated from the measuring zone, i.e. it is not thermally coupled with the measuring zone, in such a manner that the measured momentary temperature coincides at any time with the actual temperature of the measuring zone. Such a temperature sensor is hereafter called Ambient Temperature Sensor (ATS).
The electronic evaluation device of such systems includes a temperature correction unit, which is adapted to take into account the temperature prevailing at the point of time when the measurement for the determination of the result of the analysis is made. Such a correction requires, however, the coinicidence of the actual temperature in the measuring zone of the analysis element with the momentary temperature measured by the ATS at the time of measuring. This condition is not always given, in particular in home-monitoring systems as the live circumstances of the patient require analyses to be performed at different places and with changing temperature conditions. These temperature variations can cause large deviations of the momentary temperature measured by the ATS as compared to the actual temperature in the measuring zone of the test element.
In order to solve this problem, U.S. Pat. No. 5,972,715 proposes to apply a temperature measurement field, coated with a thermochromic liquid crystal (TLC), at the support of the test element in the evaluation apparatus, or at the test element itself. The temperature of the TLC is obtained by a photometric measurement. The difference between the measured temperature and the actual temperature in the measuring zone are said to be minimized by locating the temperature measuring point in close vicinity to the measuring zone of the test element. This can, however, only be achieved with sufficient exactness if the test element itself is coated with the TLC. This leads to considerable additional cost for the production of the test elements. Furthermore, an acceptable exactness of the temperature measurement can only be obtained with expensive measurement equipment.
It is an object of the invention to provide an analysis system which allows an increased measurement accuracy by an improved temperature compensation. This shall be achieved in a way which complies with the requirements of home-monitoring systems. In particular, this improvement shall not lead to a significant increase of the weight, the size or the battery consumption of the evaluation apparatus.
With an analysis system of the previously described type, this problem is solved by the fact that the temperature correction unit includes a temperature history imaging device, which traces the temperature history preceding the time of the measurement in a currentless manner, i.e. without using electric energy up to the time of measurement.
The temperature history imaging device allows to take into account, in the evaluation of the measurement signal and calculation of the result of the analysis, the temperature history in the vicinity of the apparatus before the point of time in which the measurement is made. This provides a substantially improved information about the actual temperature in the area of the measurement zone of the test element. If, for example, the evaluation apparatus was brought from a cold ambient (e.g. a car parked outdoors at a temperature of 10° C.) into a considerably warmer ambient (e.g. a living room with a temperature of 20° C.), this large temperature increase is indicated by the temperature history imaging device. In this case, it must be assumed that the momentary temperature indicated by an ATS does not correspond to the actual ambient temperature (thus, there is no thermal equilibrium to the ambient). The temperature in the measuring zone of the test element follows ambient temperature changes much faster than an ATS fixed in the apparatus housing, because the heat transfer from the ambient to the test zone is relatively good and the heat capacity of the test element is relatively small. The corresponding delay of the momentary temperature measured in the apparatus as compared to the actual temperature of the measurement zone, can be estimated using the output of the temperature history imaging device and correspo
Haar Hans-Peter
Meacham George B. K.
Alexander Lyle A.
Roche Diagnostics Corporation
Roche Diagnostics Corporation
Subramaniam Sujatha
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