Method of determining the concentration of an analyte in a sample of a body fluid

Patent metadata

Field	Value
Publication number	US-2023103160-A1
Application number	US-202218063492-A
Country	US
Kind code	A1
Filing date	Dec 8, 2022
Priority date	Jun 9, 2020
Publication date	Mar 30, 2023
Grant date	—

Abstract

A method of determining the concentration of an analyte in a sample of a body fluid with a mobile device having a camera is disclosed. The camera captures an image of a color reference card and of a reagent test field of an optical test strip having a sample applied to it. A predetermined pixel-based mean tone map correction is applied to the image obtained, which results in a first intensity-corrected image. Local brightness information is derived from the first intensity-corrected image. A mobile device-specific tone map correction is applied to the first intensity-corrected image, taking into account the local brightness information. A second intensity-corrected image is thereby obtained. Analyte concentration is determined based on a color formation reaction of the test field by using the second intensity-corrected image. Optionally, a color correction may be derived and applied to the second intensity-corrected image to obtain an intensity-corrected and color-corrected image.

First claim

What is claimed is:

1 . A method of determining the concentration of an analyte in a sample of a body fluid using a mobile device having a camera, the method comprising:
i) using the camera to capture an image of at least a part of a color reference card and of at least a part of a reagent test field of an optical test strip having the sample applied thereto,
wherein the test field is in a defined position in the image relative to the color reference card and the color reference card has a plurality of different gray reference fields locally assigned to the test field,
wherein the plurality of gray reference fields and the test field are locally assigned to each other by being placed in neighboring positions, or wherein the plurality of gray reference fields locally assigned to the test field are arranged on the color reference card such that the plurality of gray reference fields surrounds the test field,
wherein the color reference card has a plurality of different color reference fields having known reference color values and a plurality of different gray reference fields locally assigned to the color reference fields, and
wherein the plurality of gray reference fields and the color reference fields are locally assigned to each other by being placed in neighboring positions or wherein the plurality of gray reference fields locally assigned to the color reference fields are arranged on the color reference card such that the plurality of gray reference fields surrounds the color reference fields,
ii) applying a predetermined pixel-based mean tone map correction to the image obtained in step i), thereby obtaining a first intensity-corrected image, wherein the predetermined pixel-based mean tone map correction comprises an assignment of a second brightness value to a first brightness value, wherein the first brightness value is recorded by the camera, wherein each pixel of the recorded image is corrected individually by the predetermined pixel-based mean tone map correction, wherein the mean tone map correction is derived by combining a plurality of tone map corrections for different types of mobile devices; iii) deriving, from the first intensity-corrected image, local brightness information for at least some of the color reference fields and for the test field by using the gray reference fields locally assigned to the color reference fields and the test field, respectively, wherein the local brightness information comprises a numerical indication describing the local intensity of at least one RGB color of the color reference fields and the test field, respectively; iv) applying a mobile device-specific tone map correction to the first intensity-corrected image taking into account the local brightness information and thereby obtaining at least one second intensity-corrected image; and v) determining the analyte concentration based on a color formation reaction of the test field by using the second intensity-corrected image.

2 . The method according to claim 1 , further comprising:
vi) deriving a color correction by using at least some of the color reference fields in the second intensity-corrected image; and vii) applying the color correction to the second intensity-corrected image and thereby obtaining an intensity-corrected and color-corrected image.

3 . The method according to claim 2 , further comprising, prior to step vi), local white balancing at least some of the color reference fields and the test field.

4 . The method according to claim 2 , wherein, in step vi), the color correction is derived using a selection of the color reference fields based on at least one of:
selecting color reference fields in a predetermined subspace of the color space; dynamically selecting color reference fields in an environment of the color of the test field in the color space; weighting color reference fields differently; and selecting color reference fields in accordance with an accuracy of the color correction.

5 . The method according to claim 1 , wherein the pixel-based mean tone map correction comprises at least one of: a mean tone map correction derived by combining a plurality of tone map corrections for different types of mobile devices, and an inverse of a standard Gamma correction.

6 . The method according to claim 1 , further comprising performing a statistical modification of the first intensity-corrected image, wherein step iv) is performed on the basis of the statistically modified first intensity-corrected image.

7 . The method according to claim 1 , wherein the gray reference fields locally assigned to the test field surround the test field and form a test field group.

8 . The method according to claim 7 , wherein the test field group comprises a plurality of redundant gray reference fields having at least three different gray levels, wherein at least two of the redundant gray reference fields are provided for each gray level, wherein the redundant gray reference fields are arranged symmetrically around the test field, wherein, in step iii), the local brightness information for the test field is determined by averaging over redundant gray reference fields having the same gray level.

9 . The method according to claim 1 , wherein the gray reference fields locally assigned to the color reference fields surround the respective color reference fields and form a local color reference field group.

10 . The method according to claim 9 , wherein each local color reference field group comprises a plurality of redundant gray reference fields having at least three different gray levels, wherein at least two of the redundant gray reference fields are provided for each gray level, wherein the redundant gray reference fields are arranged symmetrically around the color reference field of the respective local color reference field group.

11 . The method according to claim 10 , wherein, in step iii), the local brightness information for the respective local color reference field group is determined by averaging over redundant gray reference fields having the same gray level.

12 . A mobile device having a camera and a processor, the mobile device configured for performing the method according to claim 1 .

13 . A kit for determining the concentration of an analyte in a sample of a body fluid, the kit comprising:
a mobile device having a processor and configured to perform the method according to claim 1 ; an optical test strip having a reagent test field; a color reference card having a plurality of different gray reference fields locally assigned to the test field, and wherein the color reference card comprises a plurality of different color reference fields having known reference color values and a plurality of different gray reference fields locally assigned to the color reference fields.

14 . A non-transitory computer readable medium having stored thereon computer-executable instructions for performing the method of claim 1 .

Assignees

• Roche Diabetes Care Inc

Inventors

• Berg Max
• Hailer Fredrik
• Limburg Bernd
• Tuerck Volker
• Winkelnkemper Momme

Classifications

• A61B5/145 Primary

  Measuring characteristics of blood in vivo, e.g. gas concentration or pH-value {; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid or cerebral tissue} (non-radiation detecting or locating of foreign bodies in blood A61B5/06) · CPC title

• H04N1/60 Primary

  Colour correction or control {(H04N1/54 takes precedence)} · CPC title

• G01N21/293

  with colour charts, graduated scales or turrets · CPC title

• G06T2207/10024

  Color image · CPC title

• G01N2021/8488

  the band presenting reference patches · CPC title