Analyte determination method and analyte meter
Inventors
Harding, Ian • Williams, Richard • Iyengar, Sridhar
Assignees
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Publication Number
US-7964089-B2
Publication Date
2011-06-21
Expiration Date
Abstract
The presence of oxygen or red blood cells in a sample applied to an electrochemical test strip that makes use of a reduced mediator is corrected for by an additive correction factor that is determined as a function of the temperature of the sample and a measurement that reflects the oxygen carrying capacity of the sample. The measured oxygen carrying capacity can also be used to determine hematocrit and to distinguish between blood samples and control solutions applied to a test strip.
Core Innovation
The invention provides an electrochemical determination of an analyte in a sample using a reduced mediator, where an uncorrected analyte result is obtained in an electrochemical test cell having a working electrode and a counter electrode. Oxygen in the sample provides an oxygen interferent that affects the analyte determination and is corrected by modifying the uncorrected result with an additive correction factor for the amount of oxygen in the sample.
The additive correction factor is determined as a function of the temperature of the sample and a measurement that reflects the oxygen carrying capacity of the sample. For blood samples, the measurement that reflects the oxygen carrying capacity is hematocrit (hct), and the additive correction factor is expressed as constant·[(S·T)+I]·hct, where T is the temperature and S and I are the slope and intercept of a plot in which the y axis is the slope of a line plotting uncorrected analyte measurement as a function of hematocrit and the x axis is temperature.
The oxygen-carrying-capacity measurement is obtained using mediator mobility and/or hematocrit based on a decay rate determined after switching off applied potential. A chemical potential gradient is established between electrodes, the applied potential is switched off at a time t_switch, and a value indicative of the rate of decay of the chemical potential gradient in the absence of applied potential is obtained.
Claims Coverage
Independent claims cover four related inventive features: electrochemical analyte determination with oxygen interference correction, a meter apparatus for performing the correction, blood-versus-control identification by decay-rate thresholding, and an apparatus that processes a test sample versus a calibration run based on that identification.
Additive oxygen correction as a function of temperature and oxygen carrying capacity
Determining an additive correction factor for the amount of oxygen in the sample as a function of the temperature of the sample and a measurement that reflects the oxygen carrying capacity of the sample, and modifying the uncorrected result with the correction factor to provide a corrected determination of analyte.
Electrochemical hematocrit determination via chemical potential gradient decay after switching off applied potential
Determining an oxygen carrying capacity measurement of hematocrit by applying a potential for a period sufficient to establish a chemical potential gradient between electrodes, switching off the applied potential at a time t_switch, and obtaining a value indicative of the rate of decay of the chemical potential gradient in the absence of applied potential.
Decay-rate measurement relative to a predetermined voltage and derived time indicator
Determining a value indicative of the rate of decay as a decay-time indicator by measuring the time required for the potential to decay to a predetermined voltage (V_mob) and using t_mob = t_meas − t_switch.
Meter apparatus configured to apply the oxygen-dependent additive correction
A meter apparatus comprising a housing slot for receiving an electrochemical test strip and communications means, and means for determining an uncorrected result for analyte determination, determining an additive correction factor for the amount of oxygen in the sample, and modifying the uncorrected result with the correction factor to provide a corrected determination.
Sample-type identification by decay-rate threshold comparison for blood versus control solution
Identifying whether the material applied to the electrochemical test strip is a blood sample or a control solution by establishing a chemical potential gradient between electrodes with an applied potential, switching off the applied potential at a time t_switch, obtaining a value indicative of the rate of decay of the chemical potential gradient in the absence of applied potential, and comparing the determined value with a threshold.
Apparatus processing test sample versus calibration run based on blood/control identification
An apparatus for determination of analyte in which a material may be either a blood sample or a control solution and the signal from the test strip is processed as a test sample or a calibration run based on identification.
The independent claims collectively cover electrochemical analyte determination where an uncorrected mediator-based analyte result is corrected using an additive oxygen correction factor computed from sample temperature and an oxygen-carrying-capacity metric, including hematocrit, and they also cover determining the oxygen-carrying-capacity metric and identifying blood versus control by comparing a decay-rate value to a threshold.
Stated Advantages
Not explicitly described in patent.
Documented Applications
Not explicitly described in patent.
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