A method for determining the presence of an analyte in a fluid is described along with various components of an apparatus specifically designed to carry out the method. The method involves taking a reflectance reading from one surface of an inert porous matrix impregnated with a reagent that will interact with the analyte to produce a light-absorbing reaction product when the fluid being analyzed is applied to another surface and migrates through the matrix to the surface being read. Reflectance measurements are made at two separate wavelengths in order to eliminate interferences, and a timing circuit is triggered by an initial decrease in reflectance by the wetting of the surface whose reflectance is being measured by the fluid which passes through the inert matrix. The method and apparatus are particularly suitable for the measurement of glucose levels in blood without requiring separation of red blood cells from serum or plasma.

Minimum procedure system for the determination of analytes

A whole blood glucose test strip for measuring glucose in an unmeasured whole blood sample which does not require removal of excess sample, and which is adapted for use in a reflectance reading apparatus which measures reflectance at about 635 nm and about 700 nm, the test strip comprising a handle having an aperture defined therein; and a porous, hydrophilic matrix disposed over the aperture such that one surface of the matrix is exposed to the atmosphere adjacent to one side of the strip and the other surface of the matrix is exposed to the atmosphere on the other side of the strip through the aperture, one of the surfaces being an upper sample receiving surface adapted to receive the whole blood sample on one side of the matrix and the second of the surfaces being a lower testing surface from which diffuse reflected light is measurable, the testing surface being opposite to the sample receiving surface. The matrix allows the blood color of the blood sample to be observed from the testing surface, allows at least a portion of the blood sample to penetrate through the matrix from the sample receiving surface to the testing surface, and filters out red blood cells such that they do not reach the testing surface. The matrix comprises reagent means for chemically reacting with glucose to create a change in reflectance which is indicative of the concentration of glucose present in the sample.

Whole blood glucose test strip

The present invention provides a method of measuring an analyte, such a glucose in a fluid sample, such as whole blood, by a reflectance reading device (Figure 1). The method includes making periodic intermediate calculations of analyte level and dynamically ascertaining when an analytical reaction has reached an end point. Once stable, the process stops making periodic calculations and reports the final, actual glucose concentration. According to an exemplary embodiment, the method is performed by a reflectance photometer (10) using an analytical test strip (40) containing reagents that react with an analyte of interest in the test fluid. The end point is determined by calculating an intermediate analyte level of the testing element at predetermined intervals and calculating a ratio value corresponding to the (n)th measurement to an (n-5)th measurement. When two consecutive ratio values are less than or equal to a predetermined value, the end point is deemed reached and the final analyte level ascertained.

Method for determining concentration of an analyte in a test strip

A method and apparatus for strip insertion detection in an analytical meter system. The invention allows for individual meter calibration, adaptive thresholding and ambient light correction. Increased performance is economically realized, while providing enhanced meter accuracy in varying light conditions.

Method of strip insertion detection

A method and apparatus for automatically selecting test types for an analytical meter system based on the insertion into the meter of a test element. The test element can be an analytical element, formed by a test strip with a fluid such as blood applied thereto; a control element, formed by a test strip with control fluid applied thereto; or a standard element, or a standard strip exhibiting known optical properties. By inserting the test element into the analytical meter system, optical properties are measured and the existence of relationships between the measurements are ascertained. Based on the existence or nonexistence of certain relationships, the proper test can be automatically selected by the meter without the need for user interaction. Advantageously, the results of the test can be classified and stored according to test type.

Distinguishing test types through spectral analysis

Apparatus for detecting a peak value of an analog signal includes a first counter for counting pulses from a digital clock for successive samplings of the analog signal to convert each sample of the analog signal into digital form and a counting register into which the pulse count in the first counter is transferred to be recounted at a later sampling. With a prior digital count in the register, the digital clock simultaneously (1) increments the counter to count the current signal sampling and (2) decrements the register to zero to recount the prior signal sampling. The counter is constrained to count up until both counting and recounting steps are complete before the count in the counter is transferred to the register. In this manner the counter will always attain the greater of the current and the prior sampling pulse count values and this maximum value will always be transferred into the register. A peak is signaled when the prior maximum pulse count exceeds current pulse counts for a predetermined number of successive samplings.

Method and apparatus for detecting a peak value of an analog signal

A device for starting and operating gas discharge tubes including a DC-to-AC inverter which generates a low voltage or a high voltage at an output thereof in response to first or second input signals, respectively. The output of the inverter is connected to a gas discharge tube and sensing means generates a signal proportional to the current flow through the tube. Suitable means provides a trigger or synchronizing signal to a driver. The driver, responsive to the sensed output signal and the trigger or synchronizing signal, generates a drive signal synchronized with the trigger or synchronizing signal and having a duration inversely related to the magnitude of the current flowing through the gas discharge tube. A high voltage switch applies a second input signal to the inverter in response to the drive signal to provide a decreasing high voltage duration during successive cycles of the inverter as the tube begins to conduct current. The device further includes a first input signal source which applies the low voltage input signal to the inverter such that the inverter provides low voltage to the tube when the drive signal is not present.

LeRoy D. Barter

Papers

Method and apparatus for detecting a peak value of an analog signal

Device for starting and operating gas discharge tubes