Assay test strips with multiple labels and reading same

Abstract

In one aspect, an assay test strip includes a test label that specifically binds a target analyte and a control label that is free of any specific binding affinity for the target analyte and has a different optical characteristic than the test label. In another aspect, an assay test strip includes a test label that specifically binds a target analyte and at least one non-specific-binding label that is free of any specific binding affinity for the target analyte. Systems and methods of reading assay test strips also are described.

What is claimed is: 
     
         1 . A method comprising:
 providing an assay test strip for measuring a target analyte in a fluid sample, the assay test strip configured to be contacted with the fluid sample, wherein the assay test strip comprises:
 a flow path; 
 a sample receiving zone coupled to the flow path; 
 at least one test label that specifically binds a target analyte; 
 at least one control label that specifically binds an immobilized control reagent; 
 at least one compensation label comprising a labeling substance and a probe substance that is free of any specific binding affinity for the target analyte and the immobilized control reagent; and 
 a detection zone coupled to the flow path downstream of the sample receiving zone and comprising at least one capture region including at least one immobilized reagent that specifically binds the target analyte and at least one immobilized reagent that specifically binds the at least one control label; 
   providing a reader comprising a light source, a light detector, and a data analyzer, the data analyzer configured to determine, after the assay test strip is contacted with the fluid sample:
 a test measurement value from light intensity measurements obtained from the at least one test label; 
 a control measurement value from light intensity measurements obtained from the at least one control label; and 
 a compensation measurement value from light intensity measurements obtained from the at least one compensation label. 
   
     
     
         2 . The method of  claim 1 , wherein the test measurement value corresponds to a statistical measure that is computed from the light intensity measurements obtained from the at least one test label. 
     
     
         3 . The method of  claim 1 , wherein the compensation measurement value corresponds to a statistical measure that is computed from one or more regions of the detection zone that are free of immobilized reagents. 
     
     
         4 . The method of  claim 1 , wherein the data analyzer is further configured to determine a parameter value based on the test measurement value and the compensation measurement value. 
     
     
         5 . The method of  claim 4 , wherein the parameter value is based on a ratio of the test measurement value and the compensation measurement value. 
     
     
         6 . The method of  claim 4 , wherein the parameter value is based on a difference between the test measurement value and the compensation measurement value. 
     
     
         7 . The method of  claim 4 , wherein the parameter value is based on a comparison of the test measurement value and the compensation measurement value relative to a threshold. 
     
     
         8 . The method of  claim 4 , wherein the parameter value is a relative quantity of the target analyte determined by comparing the test measurement value to the compensation measurement value. 
     
     
         9 . The method of  claim 4 , wherein the parameter value is an absolute quantity of the target analyte determined by correcting the test measurement value based on the compensation measurement value, and wherein the data analyzer is further configured to compare the corrected test measurement value to a calibration table that maps corrected test measurement values to target analyte quantities. 
     
     
         10 . The method of  claim 9 , wherein the calibration table is derived from light intensity measurements obtained from one or more calibration regions on the test strip. 
     
     
         11 . The method of  claim 1 , wherein the at least one compensation label is capable of compensating for effects of non-specific binding of the test label on light intensity measurements of the test label. 
     
     
         12 . The method of  claim 1 , wherein the detection zone is free of immobilized reagents that specifically bind the compensation label. 
     
     
         13 . The method of  claim 1 , wherein the at least one test label, the at least one control label, and the at least one compensation label are intermixed in the sample receiving zone. 
     
     
         14 . The method of  claim 1 , wherein the data analyzer is configured to determine a test measurement value after the light source focuses a beam of light onto an area of the detection zone. 
     
     
         15 . The method of  claim 1 , wherein the at least one test label comprises at least one fluorescent particle of a first type which fluoresces at a first characteristic wavelength and the compensation label comprises at least one fluorescent particle of a second type which fluoresces at a second characteristic wavelength different from the first characteristic wavelength. 
     
     
         16 . The method of  claim 1 , wherein the data analyzer is configured to determine a test measurement value after the light source scans a light beam to illuminate the detection zone. 
     
     
         17 . The method of  claim 1 , wherein the data analyzer is configured to determine a test measurement value by obtaining separable light intensity measurements from each of multiple localized regions of the detection zone.