Method of sample control and calibration adjustment for use with a noninvasive analyzer

Abstract

A method and apparatus for easing the use of an optically based noninvasive analyzer is presented. More particularly, a simplified algorithm is used that removes the daily requirement of collecting and using a noninvasive spectrum to update a calibration model. In another embodiment, a guide is used to substantially reduce variation in sample probe placement in relation to a skin tissue sampling site, resulting in the ability to maintain calibration performance with the use of a reference analyte concentration, with or without the use of a reference spectrum collected nearby in time.

1 . A noninvasive method for estimating a biological attribute concentration of human tissue of a tested subject, comprising the steps of:
 providing an apparatus for measuring light throughput, said apparatus comprising an energy source emitting light at multiple wavelengths, an input element, an output element, and a spectrum analyzer;   irradiating said tissue through said input element with multiple wavelengths of said light with resulting absorption of at least some of said wavelengths;   prior to said step of irradiating, using light sensitive elements in mechanically positioning along x- and/or y-axes said input element relative to a position of the human tissue, wherein said step of mechanically positioning aligns said input element to a targeted tissue volume;
 collecting at least a portion of non-absorbed light with said output element; determining the intensities of said collected light; 
 generating a model using calibration spectra and calibration reference concentrations; 
   adjusting said model with at least one direct reference measurement and a corresponding reference spectrum;   collecting at least one noninvasive prediction spectrum of said tissue of said tested subject;   estimating said biological attribute of said specific subject using said adjusted model; and   displaying said estimated biological attribute.   
     
     
         2 . The method of  claim 1 , wherein said biological attribute comprises a glucose concentration. 
     
     
         3 . The method of  claim 1 , wherein said light comprises wavelengths from 1100 to 1900 nm or at least one sub-range therein. 
     
     
         4 . The method of  claim 1 , wherein said noninvasive calibration spectra comprise spectra from any of:
 a single individual;   multiple individuals;   a single analyzer; and   multiple analyzers.   
     
     
         5 . The method of  claim 1 , wherein said model comprises a multivariate analysis. 
     
     
         6 . The method of  claim 5 , wherein said multivariate analysis comprises at least one of principal component regression and partial least squares. 
     
     
         7 . The method of  claim 1 , wherein use of said adjusted model occurs for a time period comprising at least one of:
 a fraction of a day;   a work day;   a waking portion of a day;   a week; and   a month.   
     
     
         8 . The method of  claim 7 , wherein said direct reference measurement comprises any of:
 a single reference glucose concentration;   a reference glucose concentration determined before or in time proximity to beginning of said time period;   the first n reference glucose concentrations of said time period; and   a set of at least two glucose concentrations.   
     
     
         9 . The method of  claim 7 , wherein said reference spectrum comprises any of
 a stored reference spectrum;   a first spectrum of said time period;   a spectrum of said specific subject;   an average of the first n spectra of said time period;   an average of the first n spectra of said specific subject;   a set of at least two spectra of said specific subject; and   a spectrum from a data base, wherein said spectrum is selected based upon at least one spectral feature.   
     
     
         10 . The method of  claim 1 , wherein said sample side of said guide comprises at least one of:
 a flat surface, and   a surface with a radius of curvature ranging from flat to 1.5 centimeters.   
     
     
         11 . The method of  claim 1 , wherein said attachment side of said guide interfaces with at least one of:
 a plug;   a photostimulator;   a sample module;   said input element; and   said output element.   
     
     
         12 . The method of  claim 1 , further comprising the step of:
 blowing air onto said fiber optic input element with a blower to evaporate moisture from said fiber optic input element.