Biosensor Systems for Determining Analyte Concentration Based On Complex Index Functions

Abstract

A biosensor system determines analyte concentration from an output signal generated from a light-identifiable species or a redox reaction of the analyte. The biosensor system adjusts a correlation for determining analyte concentrations from output signals or determined analyte concentrations with one or more complex index function extracted from the output signals or from other sources. The complex index functions determine at least one slope deviation value, ΔS, or normalized slope deviation from one or more error parameters. The slope-adjusted correlation between analyte concentrations and output signals may be used to determine analyte concentrations having improved accuracy and/or precision from output signals including components attributable to bias.

1 - 25 . (canceled) 
     
     
         26 . A biosensor system, for determining an analyte concentration in a fluid sample, comprising:
 a test sensor having a sample interface adjacent to a reservoir holding the fluid sample, wherein the test sensor generates at least one output signal responsive to the concentration of the analyte in the fluid sample; and   a measurement device having a sensor interface, a storage medium, and a processor coupled to a sensor interface and the storage medium, wherein the sensor interface is in electrical communication with the sample interface, and wherein the processor is operable to:
 determine at least one output signal value from the output signal received from the sensor interface, wherein the at least one output signal value represents an unknown concentration of the analyte in the fluid sample, 
 determine at least one ΔS value from at least a complex index function stored in the storage medium, wherein the at least one ΔS value represents a slope deviation between a slope of a correlation between analyte concentration and the at least one output signal, and a hypothetical slope of a perfect correlation between analyte concentration and output signals, the correlation between analyte concentration and the at least one output signal determined from a previously determined reference correlation between previously determined reference output signal values and reference sample analyte concentration values, the reference sample analyte concentration values obtained from a reference instrument, and 
 wherein the complex index function includes two terms, wherein each of the two terms is modified by a weighing coefficient, wherein at least one of the two terms modified by the weighing coefficients is responsive to a bias between the reference correlation of analyte concentrations and the at least one output signal, wherein the complex index function is responsive to at least one error parameter, wherein the weighing coefficients are numerical values other than one or zero, and 
 determine the analyte concentration in the fluid sample from the output signal value and a slope compensation equation stored in the storage medium, wherein the slope compensation equation adjusts a slope of at least one reference correlation with the at least one determined ΔS value. 
   
     
     
         27 . The system of  claim 26 , the test sensor arranged and configured to have a substantially linear relationship between a percent bias in an analyte concentration determined from the biosensor system and the at least one ΔS value. 
     
     
         28 . The system of  claim 27 , wherein the percent bias ((ΔA/A ref )*100%) of the determined analyte concentration is in a substantially linear relationship with the at least one ΔS value, wherein ΔA represents the difference between the corrected analyte concentration Aeon and a reference analyte concentration A ref . 
     
     
         29 . The system of  claim 26 , wherein the processor is further capable of determining the at least one ΔS value from a predictor function, the predictor function including the complex index function and one or more constants. 
     
     
         30 . The system of  claim 26 , wherein the complex index further comprises at least one constant that is not equal to zero. 
     
     
         31 . The system of  claim 26 , wherein one of the at least two terms includes at least one of a raw analyte concentration value of the sample, a temperature, or an error parameter responsive to the % Hct of the sample. 
     
     
         32 . The system of  claim 26 , wherein at least one other term of the complex index function includes the at least one error parameter, the at least one error parameter independently selected from intermediate output signal values and values external to the output signal. 
     
     
         33 . The system of  claim 32 , wherein the error parameter is responsive to error contributors causing an alteration of the at least one output signal value. 
     
     
         34 . The system of  claim 32 , wherein the processor is further operable to normalize the at least one ΔS value, wherein the normalizing is in response to a slope of a reference correlation equation or in response to a normalized slope function. 
     
     
         35 . The system of  claim 32 , wherein the at least two terms are selected by at least one exclusion test. 
     
     
         36 . The system of  claim 26 , wherein the measurement device includes a signal generator operable to generate a sequence of gated amperometry multi-pulse signals on the sensor interface and wherein the output signal is a sequence of output current values. 
     
     
         37 . The system of  claim 36 , wherein at least one of the terms of the complex index function includes a ratio of one of the output current values in the sequence to another of the output current values in the sequence. 
     
     
         38 . A method for determining an analyte concentration in a fluid sample, comprising:
 generating an output signal from a test sensor having the fluid sample in an interface adjacent to a reservoir, the test sensor inserted in a sensor interface of a measurement device; and   determining an output signal value from the output signal wherein the output signal value represents an unknown concentration of the analyte in the fluid sample;   determining a ΔS value from a complex index function stored in a storage medium, wherein the ΔS value represents a slope deviation between a slope of a correlation between analyte concentration and the output signal, and a hypothetical slope of a perfect correlation between analyte concentration and output signals, the correlation between analyte concentration and the output signal determined from a previously determined reference correlation between previously determined reference output signal values and reference sample analyte concentration values, the reference sample analyte concentration values obtained from a reference instrument, and wherein the complex index function is responsive to at least one error parameter and includes at least two terms, wherein each of the at least two terms is modified by a weighing coefficient, wherein at least one of the at least two terms modified by the weighing coefficients is responsive to a bias between the reference correlation of analyte concentrations; and   determining the analyte concentration in the sample from the output signal value and a slope compensation equation stored in the storage medium, wherein the slope compensation equation adjusts a slope of at least one reference correlation with the at least one determined ΔS value.   
     
     
         39 . The method of  claim 38 , wherein the at least one ΔS value is determined from a predictor function, the predictor function including the complex index function and one or more constants. 
     
     
         40 . The method of  claim 38 , wherein the complex index further comprises at least one constant that is not equal to zero. 
     
     
         41 . The method of  claim 38 , wherein one of the at least two terms includes at least one of a raw analyte concentration value of the sample, a temperature, or an error parameter responsive to the % Hct of the sample. 
     
     
         42 . The method of  claim 38 , wherein at least one other term of the complex index function includes the at least one error parameter, the at least one error parameter independently selected from intermediate output signal values and values external to the output signal. 
     
     
         43 . The method of  claim 42 , wherein the error parameter is responsive to error contributors causing an alteration of the at least one output signal value. 
     
     
         44 . The method of  claim 42 , further comprising normalizing the at least one ΔS value in response to a slope of a reference correlation equation or in response to a normalized slope function. 
     
     
         45 . The method of  claim 42 , further comprising selecting the at least two terms by an exclusion test. 
     
     
         46 . A method of determining an analyte concentration in a sample, comprising:
 providing a sequence of gated amperometry multiple pulse signals via a signal generator of a measurement device to a test sensor, wherein the test sensor includes a reservoir to hold the sample, and a working electrode and a counter electrode in electrical communication to the measurement device, and wherein the measurement device includes a processor, a sensor interface, a display, and a storage medium;   measuring a set of output signals, including an indicating signal for the analyte and intermediate signals in response to the sequence of gated amperometry multiple pulse signals from the working electrode responsive to the analyte of unknown concentration from the sample;   computing by the processor at least one ΔS value from at least one complex index function stored in the device storage medium, wherein the at least one ΔS value represents a slope deviation of a hypothetical slope of a perfect correlation between the analyte concentration and the output signals from the slope of the predetermined reference correlation between analyte concentration and the output signals, wherein the computing of the at least one ΔS value from at least one complex index function is from the error parameters calculated from selected intermediate output signals and dedicated measurement signals;   determining the analyte concentration by converting the indicating signal of the analyte to concentration through adjusting the reference correlation slope by the at least one ΔS value; and   displaying the output analyte concentration on the display of the measurement device.