Signal processing for measurement of physiological analytes

Abstract

A method is provided for continually or continuously measuring the concentration of target chemical analytes present in a biological system, and processing analyte-specific signals to obtain a measurement value that is closely correlated with the concentration of the target chemical analyte in the biological system. One important application of the invention involves a method for signal processing in a system for monitoring blood glucose values.

1 . A method of converting post-calibration data to provide a measurement of analyte amount or concentration in a subject, said method comprising: 
 obtaining a raw signal from the analyte, wherein (i) interstial fluid of the subject comprises said analyte, (ii) obtaining said raw signal comprises contacting said interstitial fluid with a sensing device, and (iii) said raw signal is related to analyte amount or concentration in the biological system;    subjecting the raw signal to at least one conversion step in order to convert said raw signal to an initial signal output which is indicative of the amount or concentration of analyte;    calibrating the sensing device by performing at least one calibration step that converts the initial signal output to a measurement value indicative of the amount or concentration of analyte present in the biological system; and    converting a raw signal or initial signal output obtained after the calibration of the sensing device to a measurement value indicative of the amount or concentration of analyte present in the subject.    
     
     
         2 . The method of  claim 1 , wherein after calibration of the sensing device the method further comprises obtaining a series of raw signals over time, subjecting each raw signal to at least one conversion step in order to convert said raw signal to an initial signal output which is indicative of the amount or concentration of analyte.  
     
     
         3 . The method of  claim 1 , wherein the converting the raw signal or initial signal output after the calibration of the sensing device further comprises subjecting the raw signal to at least one conversion step to convert the raw signal to an initial signal output, and converting the initial signal output to a measurement value indicative of the amount or concentration of analyte present in the subject.  
     
     
         4 . The method of  claim 1 , wherein said calibrating uses a mathematical transformation to model a relationship between a raw signal and a corresponding measurement value indicative of the amount or concentration of analyte present in the subject.  
     
     
         5 . The method of  claim 4 , wherein said mathematical transformation comprises a mathematical transformation selected from the group consisting of linear regression, non-linear regression, and neural network algorithms.  
     
     
         6 . The method of  claim 3 , wherein said calibrating uses a mathematical transformation to model a relationship between an initial signal output and a corresponding measurement value indicative of the amount or concentration of analyte present in the subject.  
     
     
         7 . The method of  claim 6 , wherein said mathematical transformation comprises a mathematical transformation selected from the group consisting of linear regression non-linear regression, and neural network algorithms.  
     
     
         8 . The method of  claim 1 , wherein said calibrating uses a single-point or multi-point calibration.  
     
     
         9 . The method of  claim 1 , wherein said converting the raw signal or initial signal output obtained after the calibration of the sensing device uses correlation factors, time corrections, and/or constants to obtain a corresponding measurement value indicative of the amount or concentration of analyte present in the subject.  
     
     
         10 . The method of  claim 1 , comprising further signal processing to refine said measurement value indicative of the amount or concentration of analyte present in the subject.  
     
     
         11 . The method of  claim 10 , wherein said further signal processing comprises a signal processing step to correct for signal differences due to variable conditions of the sensing device used to obtain the raw signal.  
     
     
         12 . The method of  claim 11 , wherein said signal processing step is used to correct for signal decline.  
     
     
         13 . The method of  claim 11 , wherein said signal processing step employs a constant offset term.  
     
     
         14 . The method of  claim 13 , wherein said offset is added to the raw signal or initial signal output to account for a non-zero signal at an estimated zero analyte concentration.  
     
     
         15 . The method of  claim 1 , wherein said sensing device comprises an electrochemical sensing element.