Error detection in analyte measurements based on measurement of system resistance
Inventors
Diamond, Steven • Harding, Ian • Williams, Richard
Assignees
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Publication Number
US-7846321-B2
Publication Date
2010-12-07
Expiration Date
Abstract
Measurement of the series track resistance of a working and counter electrode pair in an electrochemical test strip provide error detection for multiple variations in the quality of the test strip, as well as the operation of strip in the test meter. In particular, a single measurement of series resistance can be used to detect and generate an error message when an incorrect reading is likely to result due to (1) damaged electrode tracks, (2) fouled electrode surfaces, (3) dirty strip contacts, or (4) short circuit between the electrodes.
Core Innovation
The disclosed invention relates to determination of an analyte in a sample using an electrochemical test strip having working and counter electrodes, and a method that observes a current signal to provide an analyte determination. A potential difference Vapp is applied between the electrodes, and the current signal is observed for a period of time sufficient to determine a plateau current Iplateau that reflects recycling or shuttling of a mediator between the electrodes. The applied potential is then switched off at time tswitch.
After switching off the applied potential, the method determines a magnitude Vdrop of a voltage drop arising from series electrode resistance, if present. The method calculates a track resistance Rtrack, and compares the determined magnitude of Rtrack against a predetermined range. The relationship for the value of Rtrack is defined such that Rtrack = Vdrop/Iplateau, with Vdrop determined from a difference involving Vapp and either a measured potential at a predetermined time after switch-off or an electrochemical potential Velect.
The disclosure further specifies that Velect can be determined by extrapolating voltage decay observed after the potential is switched off within a defined time interval, and that the correction can use Vdrop, Vdrop-avg, or Velect as part of the resistance calculation. If the magnitude of Rtrack falls outside the predetermined range, the test is rejected and an error message is generated instead of a result. If the magnitude is within the predetermined range, the method proceeds to display or communicate the result from the analyte determination.
Claims Coverage
The partial content provides coverage for two independent claims: a method for analyte determination using an electrochemical test strip with a switched-off potential and a track-resistance-based acceptance/rejection criterion, and a corresponding meter configured to perform the same correction and error-message generation. Across the independent claims, the inventive structure is centered on (i) using a plateau current reflecting mediator recycling/shuttling, (ii) switching off the applied potential to determine a voltage drop from series electrode resistance, (iii) calculating a track resistance Rtrack from Vdrop and Iplateau, and (iv) comparing Rtrack to a predetermined range to accept or reject the test.
Track resistance correction using voltage drop after switch-off
A method applies Vapp to an electrochemical test strip, determines a plateau current Iplateau reflecting recycling or shuttling of mediator, switches off the applied potential at time tswitch, determines a voltage drop Vdrop arising from series electrode resistance, calculates Rtrack and compares the determined magnitude of Rtrack against a predetermined range, rejecting the test if outside the range.
Plateau-current-based track resistance definition from Vdrop and Iplateau
The method calculates a track resistance Rtrack, where the value of Rtrack is defined such that Rtrack = Vdrop/Iplateau, and uses the magnitude of Rtrack for acceptance/rejection by comparison to a predetermined range.
Electrode resistance-aware determination using electrochemical potential and Vdrop definition
The method determines Vdrop as a difference between Vapp and an electrochemical potential Velect, and can determine Velect by extrapolating voltage decay observed after the potential is switched off to obtain the potential value at time tswitch.
Meter for series-resistance detection and error-message output
A meter includes a housing with a slot for receiving an electrochemical test strip, communications means, means for applying a potential and determining analyte concentration from an observed current including Iplateau, means for switching off the potential at time tswitch and determining Vdrop, means for calculating Rtrack, and means for comparing Rtrack with a predetermined range and generating an error message in place of a result if Rtrack falls outside the range.
Both independent claims share the inventive acceptance/rejection logic based on calculating a track resistance Rtrack from a voltage drop Vdrop arising from series electrode resistance and a plateau current Iplateau reflecting mediator recycling/shuttling. The meter claim implements the same correction and uses the comparison to a predetermined range to generate an error message when the test is rejected.
Stated Advantages
Generates an error message in place of a result when Rtrack falls outside a predetermined range, thereby rejecting tests affected by series electrode resistance.
Allows proceeding to display or communicate the analyte determination result when Rtrack is within the predetermined range.
Documented Applications
Electrochemical analyte measurement using a disposable electrochemical test strip with working and counter electrodes, including error detection for damaged electrode tracks, fouled electrode surfaces, dirty strip contacts, and short circuits.
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