METHOD OF EVALUATING THE QUALITY OF A COLOR REFERENCE CARD

Abstract

A method of evaluating the quality of a color reference card having multiple color reference fields. The quality refers to whether the color reference card is usable for a method for determining concentration of analyte in a body fluid and/or to the degree of suitability or reliability of the color reference card for use with a method for determining analyte concentration in a body fluid. In the inventive method, an image is captured of at least a part of the color reference card using a mobile device camera. Measured color reference values are determined from the image for one or more of the color reference fields and a relationship between one or more of the measured reference color values and corresponding known reference color values is determined. The determined relationship is used to assess the quality of the color reference card. A kit and mobile device are also disclosed.

Claims

1. A method of evaluating the quality of a color reference card having multiple color reference fields with known reference values, wherein the quality of the color reference card refers to whether the color reference card is usable for a method for determining the concentration of an analyte in a body fluid and/or to the degree of suitability or the degree of reliability of the color reference card for use with a method for determining the concentration of analyte in a body fluid, the method comprising: i. capturing an image of at least a part of the color reference card using a camera of a mobile device; ii. determining measured reference color values from the image for one or more of the color reference fields; iii. determining a relationship between one or more of the measured reference color values and corresponding known reference color values; and iv. deriving an item of quality information on the quality of the color reference card using the relationship determined in step iii.

2. The method according to claim 1, wherein the determining of the relationship in step iii comprises fitting the measured reference color values to the corresponding known reference color values, wherein the deriving of the quality information in step iv comprises determining at least one fit residuum quantifying the quality of the fitting.

3. The method according to claim 1, wherein the relationship between the measured reference color values and the known reference color values comprises a color transformation matrix.

4. The method according to claim 1, wherein the item of quality information in step iv is at least partially derived using the relationship determined in step iii and by transforming measured color coordinates of a first color reference field into expected color coordinates of a second color reference field by using the relationship and by further comparing the expected color coordinates of the second color reference field with measured color coordinates of the second color reference field.

5. The method according to claim 1, wherein the item of quality information is determined by selectively leaving out measured reference color values of at least one selected color reference field in step iii, whereas color coordinates of other color reference fields are taken into account in step iii.

6. The method according to claim 5, wherein a plurality of items of quality information is determined by selectively leaving out measured reference color values of a plurality of selected color reference fields, respectively, wherein the items of quality information are compared in order to identify color reference fields having a low quality.

7. A method for determining the concentration of an analyte in a body fluid using a mobile device having a camera, an optical test strip and at least one color reference card comprising a plurality of color reference fields having known reference color values, wherein the method comprises: a. evaluating the quality of the reference card using the method according to claim 1; b. capturing an image of a reagent test region of the optical test strip having a sample of the body fluid applied thereto using the camera; and c. determining the analyte concentration based on a color formation reaction of the reagent test region taking into account the result of step a.

8. A mobile device having a camera and a processor, wherein the mobile device is configured for performing the method of evaluating the quality of a color reference card according to claim 1.

9. The mobile device according to claim 8, wherein the mobile device is further configured for determining the concentration of an analyte in a body fluid by using at least one optical test strip.

10. A kit, comprising: a mobile device having a camera and a processor, wherein the mobile device is configured for performing the method of evaluating the quality of a color reference card according to claim 1; and a color reference card comprising a plurality of color reference fields having known reference color values.

11. The kit according to claim 10, further comprising an optical test strip having at least one reagent test region.

12. A non-transitory computer readable medium having stored thereon computer-executable instructions for performing the method according to claim 1.

13. The computer readable medium according to claim 12, further comprising instructions which, when the program is executed by a mobile device, cause the processor of the mobile device to perform steps to determine analyte concentration based on a color formation reaction of a reagent test region.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0114] The above-mentioned aspects of exemplary embodiments will become more apparent and will be better understood by reference to the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0115] FIGS. 1a-b show embodiments of a color reference card in a perspective view;

[0116] FIG. 2 shows an embodiment of a mobile device and of a kit comprising the mobile device, a color reference card and an optical test strip, in a perspective view;

[0117] FIG. 3 shows a flow chart of an embodiment of a method of evaluating the quality of a color reference card; and

[0118] FIG. 4 shows a flow chart of an embodiment of a method for determining the concentration of at least one analyte in a bodily fluid.

DESCRIPTION

[0119] The embodiments described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of this disclosure.

[0120] In FIGS. 1a-b, exemplary embodiments of a color reference card 110 are shown in a perspective view. The color reference card 110 comprises a plurality of color reference fields 112 having known reference color values. The color reference fields 112 may be in an intact state, as it is visible in FIG. 1a. The color reference fields 112 may also be at least partially in a defective state, for example by being damaged, scratched or the like, as symbolically depicted by the defective color reference fields 113 in FIG. 1b.

[0121] The color reference fields 112 may be arranged on the surface of the color reference card 110, such as on a substrate of the color reference card 110. In particular, the color reference fields 112 may be distributed equally over the surface of the color reference card 110, specifically in such a way that the plurality of color reference fields 112 may be distributed over the entire surface of the color reference card 110. As an example, the color reference fields 112 may be arranged in matrix pattern, such as a rectangular matrix pattern. However, the color reference fields 112 may also be arranged in other ways, such as separately from each other. For example, the color reference card 110 may comprise a plurality of gray color reference fields 114 surrounding the color reference fields 112. The color reference fields 112 and the gray color reference fields 114 may not overlap each other. In an exemplary embodiment of the color reference card 110, the color reference fields 112 and the gray color reference fields 114 may be printed on a pre-printed gray colored background of the color reference card 110. Thus, the color reference fields 112 may overlap with the gray colored background of the color reference card 110.

[0122] The color reference card 110 may further comprise at least one window 116. Thus at least one optical test strip 118 or a part thereof may be visible through the window 116 when the color reference card 110 is placed on top of the optical test strip 118. Specifically, at least one reagent test region 120 comprised by the optical test strip 118 may be visible through the window 116 of the color reference card 110. As another example, the color reference card 110 may comprise the optical test strip 118 having at least one reagent test region 120, specifically in such a way that the at least one reagent test region 120 is accessible and visible.

[0123] Further, the color reference card 110 may comprise at least one marker 122. The marker 122 may be or may, as an example, comprise at least one of a position marker, such as an ArUco code, a barcode, a QR-code, a label or a combination thereof. In FIGS. 1a and 1b, the marker 122 specifically may comprise one or more ArUco codes, such as in the corners of a rectangular matrix comprising the color reference fields 112. Thus, generally, the marker 122 may be arranged in at least one corner 124 of the color reference card 110. For example, at least one marker 122 may be arranged in each of the corners 124 of the color reference card 110, specifically in such a way that the marker 122 may be visible together with the plurality of color reference fields 112. Further, the marker 122 may comprise information about the orientation of the color reference card 110.

[0124] In FIGS. 1a and 1b, the color reference fields 112 may comprise fields having different colors, for example, color reference fields 112 having a black color (denoted by reference number 148), color reference fields 112 having one or more gray colors (denoted by reference number 150), color reference fields 112 having a white color (denoted by reference number 152) and/or color reference fields 112 having one or more colors, such as a blue color, a green color, a red color and/or a mixed color thereof (denoted by reference number 154). The gray color reference fields 114 may comprise, similar to the color reference fields 112, fields having one or more gray colors (denoted by reference number 150).

[0125] In FIG. 2, an exemplary embodiment of a kit 126 is shown in a perspective view. The kit 126 comprises at least one mobile device 128 and at least one color reference card 110. Further, the kit 126 may comprise the at least one optical test strip 118.

[0126] The mobile device 128 may be or may comprise at least one of a cell phone, a smartphone, a tablet computer or the like. Further, the mobile device 128 has at least one camera 130. The camera 130 of the mobile device 128 may be configured for recording images, specifically color images. Thus, the camera 130 may be a color camera and may comprise at least three color sensors, such as at least one color sensor for the R, G, B colors.

[0127] Further, the mobile device 128 may comprise at least one processor 132. The processor132 may be configured, specifically by software programming, to perform one or more of the method steps of the method of evaluating the quality of the color reference card 110. Further, the processor 132 may be configured for supporting one or more of steps b. and c. of the method for determining the concentration of an analyte in a bodily fluid. Exemplary embodiments of the above-mentioned methods are shown in FIGS. 3 and 4, respectively, and will be described in further detail below. Thus, reference may be made to the description of FIGS. 3 and 4.

[0128] The processor 132 may specifically be configured for supporting the capturing of at least one image of the color reference card 110. Specifically, the processor 132 may prompt a user of the mobile device 128 to capture the image. Additionally or alternatively, the processor 132 may be configured for automatically capturing the image of the color reference card 110, specifically when the color reference card 110 may be in a field of view.

[0129] The color reference card 110 specifically may be embodied according to any one of the embodiments disclosed in FIGS. 1a-b as described in further detail above. The color reference card 110 comprises the plurality of color reference fields 112 having known reference color values. Further, the color reference card 110 may comprise the at least one window 116. Thus, the optical test strip 118 may be visible through the window 116 of the color reference card 110, specifically when the color reference card 110 may be placed on top of the optical test strip 118 such that both, the color reference card 110 and the optical test strip 118, may be visible on the at least one image captured by the camera 130 of the mobile device 128. Specifically, the at least one reagent test region 120 of the optical test strip 118 may be visible through the window 116 of the color reference card 110.

[0130] The color reference card 110 may further comprise the at least one marker 122. The marker 122 may be arranged on at least one surface of the color reference card 110 such that the marker 122 may be detectable by the camera 130 of the mobile device 128. The at least one marker 122 may be used for identifying the orientation of the color reference card 110. Specifically, the processor 132 of the mobile device 128 may be configured for detecting the marker 122 on an image captured by the camera 130 and for further retrieving information about the orientation of the color reference card 110.

[0131] FIG. 3 shows a flow chart of an exemplary embodiment of a method of evaluating the quality of a color reference card 110 (reference number 134 in FIGS. 3 and 4). The method comprises the following steps, which may specifically be performed in the given order. Still, a different order may also be possible. It may be possible to perform two or more of the method steps fully or partially simultaneously. It may further be possible to perform one, more than one or even all of the method steps once or repeatedly. The method may comprise additional method steps that are not listed.

[0132] The method comprises: [0133] i. (denoted with reference number 136) capturing at least one image of at least a part of the color reference card 110 by using the at least one camera 130 of the at least one mobile device 128; [0134] ii. (denoted with reference number 138) determining measured reference color values for at least some of the color reference fields 112 from the image; [0135] iii. (denoted with reference number 140) determining a relationship between at least some of the measured reference color values and the corresponding known reference color values; and [0136] iv. (denoted with reference number 142) deriving at least one item of quality information on the quality of the color reference card 110 by using the relationship of step iii.

[0137] In step i., the capturing of the at least one image of at least a part of the color reference card 110 may be initiated by the processor 132 of the mobile device 128. For example, the processor 132 may be configured for prompting the user to capture the image of the color reference card 110. As another example, the processor 132 may be configured for detecting the color reference card 110 in a field of view and further for automatically capturing the image by using the camera 130 of the mobile device 128.

[0138] The marker 122, which may be comprised by the color reference card 110, may be visible on the image captured in step i. Thus, the processor 132 may be configured for retrieving information about the orientation of the color reference card 110. Further, a computer vision process and/or an image analysis may be used to identify the color reference fields 112 comprised by the color reference card 110 and may determine measured reference color values for at least some of the color reference fields 112. For example, the measured reference color values may comprise color coordinates in a predetermined color coordinate system, specifically R, G, B color coordinates. By identifying color reference fields 112 on the color reference card 110, known reference color values may be assigned to the measured color reference fields 112. Thus, the mobile device 128 may comprise a data storage device which specifically may be configured for storing the known reference color values of the plurality of color reference fields 112. The known reference color values may also comprise color coordinates in a predetermined color coordinate system, for example R, G, B color coordinates.

[0139] Further, in step iii., the relationship between measured reference color values and the corresponding known reference color values is determined. Thus, step iii. may comprise fitting the measured reference color values to the corresponding known reference color values. For example, the relationship may be or may comprise a linear transformation, represented by a matrix, such as a color transformation matrix. The color transformation matrix may be used for correcting measured color values by transforming measured color values into true color values. Specifically, the color transformation matrix may be determined in step iii. by fitting the measured reference color values to the corresponding known color reference values. The color transformation matrix determined in step iii. may be used for a method of determining the concentration of an analyte in a bodily fluid as will be described in further detail below.

[0140] In step iv., the at least one item of quality information on the quality of the color reference card 110 is derived by using the relationship of step iii., specifically the color transformation matrix. As an example, step iv. may comprise determining at least one fit residuum quantifying the quality of the fitting. Specifically, the fit residuum may quantify a deviation of the fitting to measured reference color values. For example, the fit residuum may be or may comprise a sum of squared residuals.

[0141] As another example, the at least one item of quality information may at least partially be derived by using the relationship in step iii. and by transforming measured color coordinates of at least one first color reference field 112 into expected color coordinates of at least one second color reference field 112 by using the relationship, specifically by using the color transformation matrix. Thus, the item of quality information may at least partially be derived by comparing the expected color coordinates of the second color reference field 112 with measured color coordinates of the second color reference field 112.

[0142] As a further example, the at least one item of quality information may be derived by selectively leaving out measured color values of at least one selected color reference field 112 in step iii. The color coordinates of other color reference fields 112 may be taken into account in step iii. Thus, a fit residuum may be derived for a set of color reference fields 112 leaving out the one selected color reference field 112. This may be repeated at least once, twice or even more than twice, specifically in such a way that each of the color reference fields 112 may be selected once to be left out. Thereby, a plurality of items of quality information may be determined by selectively leaving out measured reference color values of a plurality of selected color reference fields 112. Thus, the items of quality information may be compared in order to identify color reference fields 112 having a low quality, specifically for identifying damaged color reference fields 112. Damaged color reference fields 112 and/or color reference fields 112 having a low quality may be excluded from determining the relationship in step iii.

[0143] The method of evaluating the quality of a color reference card 110 may be at least partially computer implemented. Specifically, the mobile device 128 may be configured for executing a computer program comprising instructions which, when the program is executed by the mobile device 128, cause the processor 132 of the mobile device 128 to perform the method of evaluating the quality of a color reference card 110.

[0144] In FIG. 4, a flow chart of an exemplary embodiment of a method for determining the analyte concentration in a bodily fluid is shown. The method comprises using the at least one mobile device 128 having the at least one camera 130. The method further comprises using the at least one optical test strip 118 and the at least one color reference card 110 comprising a plurality of color reference fields 112 having known reference color values.

[0145] The method comprises the following steps, which specifically may be performed in the given order. Still, a different order may also be possible. It may be possible to perform two or more of the method steps fully or partially simultaneously. It may further be possible to perform one, more than one or even all of the method steps once or repeatedly. The method may comprise additional method steps that are not listed.

[0146] The method comprises: [0147] a. (denoted with reference number 134) evaluating the quality of the reference card 110 using the method of evaluating the quality of a color reference card 110; [0148] b. (denoted with reference number 144) capturing at least one image of at least one reagent test region 120 of the optical test strip 118 having a sample of the bodily fluid applied thereto by using the camera 130; and [0149] c. (denoted with reference number 146) determining the analyte concentration based on a color formation reaction of the reagent test region 120, taking into account the result of step a.

[0150] In particular, evaluating the quality of the color reference card 110 in step a. of the method may comprise the method according to the exemplary embodiment described in FIG. 3 above. Thus, the following steps of the analytical measurement, specifically steps b. and c., may be performed in case the quality of the color reference card 110 has been evaluated as being a high quality. Specifically, the analytical measurement may be performed in case the item of quality information indicates that the color reference card 110 is of a high quality and, thus, the relationship determined in step iii. may be a highly accurate relationship.

[0151] Thus, the processor 132 of the mobile device 128 may receive and/or process the item of quality information derived in step iv. of the method of evaluating the quality of the color reference card 110. The processor 132 may further initiate the analytical measurement, in particular steps b. and c., in case the item of quality information indicates a high quality of the color reference card 110. For example, the processor 132 may initiate the further method steps by prompting the user to apply the sample of bodily fluid onto the reagent test region 120 of the optical test strip 118.

[0152] In step b., the capturing of the image of the reagent test region 120 may be performed by the processor 132, for example by prompting the user to capture the image and/or by automatically capturing the image.

[0153] Further, the analytical measurement may comprise detecting a color value of the reagent test region 120 having the sample of the bodily fluid applied thereto and determining the analyte concentration based on the color formation reaction of the reagent test region 120, taking into account the result of step a. Specifically, the relationship determined in step iii. may be used to correct measured color values of the color formation reaction, for example by using the color transformation matrix. The analyte concentration may be determined by using the corrected color values.

[0154] The method for determining the concentration of an analyte in a bodily fluid may at least partially be computer implemented, specifically steps b. and c. of the method. The mobile device 128 may specifically be configured for executing the computer program, which when executed by the mobile device 128, cause the processor 132 of the mobile device 128 to perform steps b. and c. of the method. The processor 132 may specifically be configured for capturing the at least one image of the reagent test region 120, such as by prompting the user to capture the at least one image and/or by automatically capturing the at least one image. For example, the image captured in step b. of the method for determining the analyte concentration of a bodily fluid may be identical to the image captured in step i. of the method of evaluating the quality of the color reference card 110. Thus, the at least one captured image may comprise at least part of the color reference card 110 and the at least one reagent test region 120 of the optical test strip 118.

[0155] Further, the processor 132 may be configured, specifically by software programming, for determining the analyte concentration based on the color formation reaction of the reagent test region 120. The processor 132 may be configured for determining the analyte concentration by evaluating the captured image, deriving a change of one or more color coordinates taking place during the color formation reaction and transforming the change of the at least one color coordinate into the analyte concentration value. Specifically, the processor 132 may be configured for using the relationship determined in step iii. of the method of evaluating the quality of the color reference card 110 for deriving a true color value from the captured image. Thus, the processor 132 may correct the measured color values of the captured image by transforming measured color values into true color values using the color transformation matrix determined in step iii. of the method of evaluating the quality of the color reference card 110.

[0156] While exemplary embodiments have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

LIST OF REFERENCE NUMBERS

[0157] 110 color reference card [0158] 112 color reference field [0159] 113 defective color reference fields [0160] 114 gray color reference field [0161] 116 window [0162] 118 optical test strip [0163] 120 reagent test region [0164] 122 marker [0165] 124 corner [0166] 126 kit [0167] 128 mobile device [0168] 130 camera [0169] 132 processor [0170] 134 evaluating the quality of a color reference card [0171] 136 capturing at least one image of at least a part of the color reference card [0172] 138 determining measured reference color values [0173] 140 determining a relationship [0174] 142 deriving at least one item of quality information [0175] 144 capturing at least one image of at least one reagent test region [0176] 146 determining the analyte concentration [0177] 148 fields of black color [0178] 150 fields of gray color [0179] 152 fields of white color [0180] 154 fields of color