Methods for determining test result validity using fluid flow transit time across a test strip

• US 10,600,178 B2
• Filed: 03/14/2013
• Issued: 03/24/2020
• Est. Priority Date: 01/15/2009
• Status: Active Grant

• Current Assignee: Alverix, Inc. (Becton, Dickinson & Co)
• Original Assignee: Alverix, Inc. (Becton, Dickinson & Co)
• Inventors: Dylewski, Scott
• Primary Examiner(s): Nguyen, Bao Thuy L
• Assistant Examiner(s): Hollinden, Gary E
• Application Number:
  US13/804,284
• Publication Number:
  US 20130196345A1
• Time in Patent Office: 2,567 Days
• Field of Search: None
• CPC Class Codes: G01F 1/7086 using optical detecting arrangements
• CPC Class Codes: G01N 21/78 producing a change of colour
• CPC Class Codes: G01N 21/8483 Investigating reagent band test-element handling not specific to a test method G01N33/4875; analytical elements specific to chemical analysis of biological material G01N33/52; autometer with reagent band G01N35/04
• CPC Class Codes: G06T 7/0012 Biomedical image inspection

Abstract

The present disclosure relates to methods for determining a wavefront position of a liquid on a surface of an assay test strip placing a liquid on the surface of the test strip; and acquiring one or more signals from the surface of the test strip at one or more times, comparing the one or more acquired signals to a threshold, wherein the wavefront position is a position on the surface of the test strip where a signal is greater than or less than a threshold (e.g., fixed or dynamic threshold). Such methods may be used to determine the wavefront velocity of a liquid on a surface of an assay test strip and the transit time of a liquid sample to traverse the one or more positions on the surface of the assay test strip.

Claims

1. A system for determining a rate of progress of a liquid to flow from a first position to a second position along a length of a test strip, said system comprising:

the test strip; and

a reader device comprising;

one or more light source or sources positioned to emit light onto a surface of the test strip;

photodetectors positioned to detect the light after reflection from the surface of the test strip, the photodetectors configured to;

acquire a first image of the surface of the test strip at a first time, the first time corresponding to a starting time at which the sample is placed in a liquid receiving zone of the test strip, the liquid receiving zone comprising the first position, the first image comprising a first plurality of pixels;

acquire a second image of the surface of the test strip at a second time after the first time, the second image comprising a second plurality of pixels; and

a central processing unit or microcontroller configured to;

determine a result indicated by the test strip;

generate a difference plot representing level of change values along the length of the test strip, a particular level of change value computed between one of the first plurality of pixels and a corresponding one of the second plurality of pixels;

identify a point on the difference plot farthest along the length of the test strip from the liquid receiving zone where the level of change value is above a threshold;

determine a wavefront position based on a location along the length of the test strip corresponding to the point;

identify a distance between the first position and the wavefront position;

calculate the rate of progress of the sample across the test strip based on the identified distance and a time elapsed between the second time and the first time;

determine whether the result is accurate based on whether the rate of progress is within a predetermined limit;

in response to determining that the rate of progress is not within the predetermined limit, disregard the result of the test strip and output a notification associated with disregarding the result of the test strip; and

in response to determining that the rate of progress is within the predetermined limit, output the result of the test strip.

2. The system of claim 1, wherein the central processing unit is configured to subtract values of the first and second plurality of pixels from a constant prior to comparing said values to the threshold value.

3. The system of claim 1, wherein the central processing unit is configured to divide values of the first and second plurality of pixels by a constant prior to comparing said values to the threshold value.

4. The system of claim 1, wherein the central processing unit is configured to compare values of corresponding pixels of the first and second plurality of pixels with each other prior to comparing said values to the threshold value.

5. The system of claim 1, wherein the central processing unit is configured to subtract values of corresponding pixels of the first and second plurality of pixels prior to comparing said values to the threshold value.

6. The system of claim 1, wherein the central processing unit is configured to divide a value of each of the first plurality of pixels by a value of a corresponding one of the second plurality of pixels prior to comparing said values to the threshold value.

7. The system of claim 1, wherein the central processing unit is configured to acquire the first image during insertion of the test strip into the reader device.

8. The system of claim 1, wherein the test strip is a lateral flow assay test strip.

9. The system of claim 1, wherein the liquid is a test sample.

10. The system of claim 1, wherein the central processing unit is configured to acquire a plurality of images of the surface of the test strip at regular intervals, wherein the first image and the second image are sequential images of the plurality of images.

11. The system of claim 1, wherein the central processing unit is configured to acquire a plurality of images of the surface of the test strip at regular intervals, wherein the first image and the second image are non-sequential images of the plurality of images.

12. The system of claim 1, wherein the test strip comprises a test zone having an immobilized capture reagent that binds to an analyte of interest in the liquid.

13. The system of claim 12, wherein the predetermined limit for the rate of progress is determined at least partly based on a length of time required for the analyte to be in contact with the immobilized capture reagent to detect a threshold amount of the analyte.

14. The system of claim 12, wherein the central processing unit is configured to:

acquire an additional image of the test zone after binding of the analyte of interest with the immobilized capture reagent; and

determine the result of the test strip based on an amount of light detected from the test zone.

15. The system of claim 14, wherein the central processing unit is configured to determine the result by determining a concentration of the analyte of interest in the liquid.

16. The system of claim 12, wherein the second position comprises the test zone.

17. The system of claim 1, wherein the second position comprises an end of the test strip opposite the liquid receiving zone.