METHODS AND DEVICES FOR PERFORMING AN ANALYTICAL MEASUREMENT

Abstract

A determination method of determining a dynamic coefficient of variation limit (Cv.sub.TR, lim) for assessing validity of an optical test strip usable for an analytical measurement based on a color formation reaction is disclosed. Training sets of optical test strips and mobile devices are provided. A color reference card is also provided. Images are captured of reagent test regions of the optical test strip and of a color reference field(s) of the reference card. A training set of pairs of reagent test region coefficients of variation (Cv.sub.TR) and corresponding minimum color reference field coefficients of variation (Cv.sub.RF, min) are determined. A relation for determining the dynamic coefficient of variation limit (Cv.sub.TR, lim) for the respective reagent test region is derived. The dynamic coefficient of variation limit (Cv.sub.TR, lim) defines a maximum coefficient of variation (Cv.sub.TR, max) for reagent test regions of non-corrupted optical test strips.

Claims

1. A determination method of determining a dynamic coefficient of variation limit (Cv.sub.TR, lim) for assessing validity of an optical test strip usable for an analytical measurement based on a color formation reaction, the method comprising: a) providing a training set of optical test strips, each having a reagent test region, wherein at least two of the optical test strips are non-corrupted and at least two of the optical test strips are corrupted; b) providing a training set of mobile devices, each mobile device having a camera; c) providing a color reference card having a plurality of color reference fields with known reference color values; d) capturing, by using the mobile devices of the training set of mobile devices, a training set of images, wherein each image of the training set of images comprises at least a part of at least one reagent test region of an optical test strip of the training set of optical test strips and at least a part of at least one color reference field of the color reference card; e) determining, for at least one color channel of the cameras of the mobile devices of the training set of mobile devices, a training set of pairs of reagent test region coefficients of variation (Cv.sub.TR) and corresponding minimum color reference field coefficients of variation (Cv.sub.RF, min), wherein each reagent test region coefficient of variation (Cv.sub.TR) is determined by measuring a color variation within the reagent test region, wherein each color reference field coefficient of variation (Cv.sub.RF) is determined by measuring a color variation within the color reference field, wherein a minimum color reference field coefficient of variation (Cv.sub.RF, min) for the corresponding reagent test region coefficient of variation (Cv.sub.TR) is determined by comparing the color reference field coefficients of variation (Cv.sub.RF) of the color reference fields of which a common image was captured together with the corresponding reagent test region; and f) deriving, from the training set of pairs of reagent test region coefficients of variation (Cv.sub.TR) and corresponding minimum color reference field coefficients of variation (Cv.sub.RF, min), a relation for determining the dynamic coefficient of variation limit (Cv.sub.TR, lim) for the respective reagent test region by using the corresponding measured minimum color reference field coefficient of variation (Cv.sub.RF, min), wherein the dynamic coefficient of variation limit (Cv.sub.TR, lim) defines a maximum coefficient of variation (Cv.sub.TR, max) for reagent test regions of non-corrupted optical test strips.

2. The method according to claim 1, wherein the method further comprises step g) of applying a sample of body fluid to the reagent test region of the optical test strip.

3. The method according to claim 1, wherein the method further comprises step h) of attaching at least one of the optical test strips of the training set to the color reference card, wherein step h) is performed before step d).

4. The method according to claim 1, wherein one of the corrupted optical test strips is corrupted by at least one of: a previous appliance of a fluid sample; a previous exposure to at least one corruptive environment for more than 10 minutes; a time elapsed since application of a fluid sample being out of a tolerance range.

5. The method according to claim 4, wherein the corruptive environment is selected from the group consisting of a humid environment and a bright environment.

6. The method according to claim 1, wherein step e) further comprises labelling the pairs of reagent test region coefficients of variation (Cv.sub.TR) and corresponding minimum color reference field coefficients of variation (Cv.sub.RF, min) of the training set of pairs of reagent test region coefficients of variation (Cv.sub.TR) and corresponding minimum color reference field coefficients of variation (Cv.sub.RF, min) with information on whether the respective optical test strip of the training set of optical test strips was corrupted or non-corrupted.

7. The method according to claim 1, wherein in step f) the dynamic coefficient of variation limit (Cv.sub.TR, lim) excludes at least 90% of the corrupted optical test strips of the training set of optical test strips.

8. The determination method according to claim 1, wherein in step f) the dynamic coefficient of variation limit (Cv.sub.TR, lim) permits acceptance of at least 80% of the non-corrupted optical test strips of the training set of optical test strips.

9. The determination method according to claim 1, wherein the relation derived in step f) comprises a linear function.

10. A measurement method of performing an analytical measurement based on a color formation reaction by using a mobile device having a camera and a processor, the method comprising: i) providing at least one optical test strip having at least one reagent test region; ii) providing a color reference card having a plurality of color reference fields having known reference color values; iii) capturing, by using the camera, an image of at least a part of the reagent test region having a sample of body fluid applied thereto and at least a part of at least one of the color reference fields of the color reference card; iv) determining, for at least one color channel of the camera of the mobile device, a color reference field coefficient of variation (Cv.sub.RF) for at least one of the color reference fields by using the image, wherein the color reference field coefficient of variation (Cv.sub.RF) is determined by measuring a color variation within the at least one color reference field; v) determining a minimum color reference field coefficient of variation (Cv.sub.RF, min) for the color reference card by using the at least one color reference field coefficient of variation (Cv.sub.RF) determined in step iv); vi) determining a dynamic coefficient of variation limit (Cv.sub.TR, lim) for the reagent test region by using the minimum color reference field coefficient of variation (Cv.sub.RF, min) determined in step v) and by using a relation for determining the dynamic coefficient of variation limit (Cv.sub.TR, lim), wherein the relation is determined by performing the determination method according to claim 1; vii) determining, for the at least one color channel, a reagent test region coefficient of variation (Cv.sub.TR) of the reagent test region by using the image, wherein the reagent test region coefficient of variation (Cv.sub.TR) is determined by measuring a color variation within the reagent test region; viii) comparing, for the at least one color channel, the reagent test region coefficient of variation (Cv.sub.TR) to the determined dynamic coefficient of variation limit (Cv.sub.TR, lim) for the reagent test region; ix) when the reagent test region coefficient of variation (Cv.sub.TR) is larger than the dynamic coefficient of variation limit (Cv.sub.TR, lim), considering the optical test strip to be corrupted and aborting the measurement method; and x) when the reagent test region coefficient of variation (Cv.sub.TR) is smaller than the dynamic coefficient of variation limit (Cv.sub.TR, lim), considering the optical test strip to be non-corrupted and determining a concentration of at least one analyte in the sample of body fluid by using, for the at least one color channel, at least one color formation value for a color formation of the reagent test region having at least one sample of at least one body fluid applied to the reagent test region of the optical test strip.

11. The measurement method according to claim 10, further comprising at least one step of applying the sample of body fluid to the reagent test region of the optical test strip, wherein the dynamic coefficient of variation limit (Cv.sub.TR, lim) in step vi) is determined by using a relation derived with the sample of the body fluid applied to the reagent test regions of the optical test strips of the training set of optical test strips, wherein the measurement method comprises applying the sample of body fluid to the reagent test region before step iii).

12. The measurement method according to claim 10, further comprising at least one step of applying the sample of body fluid to the reagent test region of the optical test strip, wherein the dynamic coefficient of variation limit (Cv.sub.TR, lim) in step vi) is determined by using a relation derived with no sample of the body fluid applied to the reagent test regions of the optical test strips of the training set of optical test strips, wherein the measurement method comprises performing steps iii) to viii) with no sample of the at least one body fluid applied to the reagent test region of the optical test strip, and wherein the method further comprises applying the at least one sample of the body fluid to the reagent test region of the optical test strip before or during performing step x).

13. A determination system for determining a dynamic coefficient of variation limit (Cv.sub.TR, lim) for assessing validity of an optical test strip usable for an analytical measurement based on a color formation reaction, comprising: A) a training set of optical test strips each having a reagent test region, wherein at least two of the optical test strips are non-corrupted and wherein at least two of the optical test strips are corrupted; B) a training set of mobile devices, each mobile device having a camera; C) a color reference card having a plurality of color reference fields having known reference color values; D) a processor configured for: retrieving a training set of images captured with the camera, wherein each image of the training set of images comprises at least a part of a reagent test region of an optical test strip of the training set of optical test strips and at least a part of at least one color reference field of the color reference card; determining, for at least one color channel of the cameras of the mobile devices of the training set of mobile devices, a training set of pairs of reagent test region coefficients of variation (Cv.sub.TR) and corresponding minimum color reference field coefficients of variation (Cv.sub.RF, min), wherein each reagent test region coefficient of variation (Cv.sub.TR) is determined by measuring a color variation within the reagent test region, wherein each color reference field coefficient of variation (Cv.sub.RF) is determined by measuring a color variation within the color reference field, wherein a minimum color reference field coefficient of variation (Cv.sub.RF, min) for the corresponding reagent test region coefficient of variation (Cv.sub.TR) is determined by comparing the color reference field coefficients of variation (Cv.sub.RF) of the color reference fields of which a common image was captured together with the corresponding reagent test region; and deriving, from the training set of pairs of reagent test region coefficients of variation (Cv.sub.TR) and corresponding minimum color reference field coefficients of variation (Cv.sub.RF, min), a relation for determining the dynamic coefficient of variation limit (Cv.sub.TR, lim) for the respective reagent test region by using the corresponding measured minimum color reference field coefficient of variation (Cv.sub.RF, min), wherein the dynamic coefficient of variation limit (Cv.sub.TR, lim) defines a maximum coefficient of variation (Cv.sub.TR, max) for reagent test regions of non-corrupted optical test strips.

14. A computer-readable storage medium comprising instructions which, when executed by a determination system, cause the determination system to carry out at least steps e) and f) according to claim 1.

15. A mobile device having a camera and a processor, the mobile device being configured for performing at least steps iv) to x) of the measurement method according to claim 10.

16. A computer-readable storage medium comprising instructions which, when executed by a mobile device having a camera and a processor, cause the mobile device to carry out at least steps iv) to x) of claim 10.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0177] 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:

[0178] FIG. 1 schematically shows an exemplary embodiment of a determination system according to this disclosure;

[0179] FIG. 2 schematically shows an exemplary embodiment of a mobile device;

[0180] FIG. 3 shows a flow chart of an embodiment of a determination method;

[0181] FIG. 4 shows experimental data referring to an embodiment of a determination method;

[0182] FIG. 5 shows a flow chart of an embodiment of a measurement method; and

[0183] FIG. 6 shows experimental data referring to an embodiment of a measurement method.

DESCRIPTION

[0184] 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.

[0185] FIG. 1 schematically shows an exemplary embodiment of a determination system 110 for determining a dynamic coefficient of variation limit (Cv.sub.TR, lim) for assessing validity of an optical test strip 112 usable for an analytical measurement based on a color formation reaction. The determination system 110 comprises a training set 111 of optical test strips 112. Each optical test strip 112 has a reagent test region 114. At least two of the optical test strips 112 are non-corrupted. At least two of the optical test strips 112 are corrupted. FIG. 1 exemplarily shows two non-corrupted optical test strips 116 and two corrupted optical test strips 118. In principle, the training set 111 of optical test strips 112 may specifically comprise an even larger number of optical test strips 112, specifically for better statistics. FIG. 1 exemplarily indicates a grid pattern 120 in the reagent test region 114 of the corrupted optical test strips 118. Typically, applied blood produces such a grid pattern 120 in the reagent test region 114 if there already has been blood applied on the reagent test region 114 previously, which increases an inhomogeneity of the reagent test region 114. In other words, the grid pattern 120 typically shows up, when a previously used optical test strip 112 is used again. Thus, the grid pattern 120 typically indicates a previous use corrupting the optical test strip 112. However, other options are also conceivable. As an example, the grid pattern 120 may also be a result of an intense light exposure which may also corrupt the optical test strip 112.

[0186] Generally, the corrupted optical test strip 118 may be corrupted by at least one of: a previous appliance of a fluid sample, specifically a sample of bodily fluid; a previous exposure to at least one corruptive environment for more than 10 minutes, specifically for more than 2 hours, more specifically for more than 1 day; a time elapsed since application of a fluid sample being out of a tolerance range, specifically a time between sample application and capturing of an image. The corruptive environment may be selected from the group consisting of: a humid environment, specifically an environment having a humidity of more than 60%, more specifically a humidity of more than 80%, and a bright environment, specifically an environment having an illuminance of more than 1000 lm/m.sup.2, more specifically an illuminance of more than 1500 lm/m.sup.2.

[0187] The determination system 110 further comprises a training set 121 of mobile devices 122. Each mobile device 122 has at least one camera 124. In principle, the training set 121 of mobile devices 122 may specifically comprise an even larger number of mobile devices 122, specifically for better statistics. The mobile device 122 may be or may comprise at least one of a cell phone, a smart phone, a tablet computer or the like. The camera 124 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.

[0188] The determination system 110 further comprises at least one color reference card 126. The color reference card 126 has a plurality of color reference fields 128. The color reference fields 128 have known reference color values. The color reference fields 128 may be arranged on a surface of the color reference card 126, such as on a substrate of the color reference card 126. In particular, the color reference fields 112 may be distributed equally over the surface of the color reference card 126, specifically in such a way that the plurality of color reference fields 126 may be distributed over the entire surface of the color reference card 126. As an example, the color reference fields 128 may be arranged in matrix pattern, such as a rectangular matrix pattern. However, the color reference fields 128 may also be arranged in other ways, such as separately from each other. For example, the color reference card 126 may comprise a plurality of gray color reference fields 130 surrounding the color reference fields 128. The color reference fields 128 and the gray color reference fields 130 may not overlap each other. In an exemplary embodiment of the color reference card 126, the color reference fields 128 and the gray color reference fields 130 may be printed on a pre-printed gray colored background of the color reference card 126. Thus, the color reference fields 128 may overlap with the gray colored background of the color reference card 126.

[0189] The color reference card 126 may further comprise at least one window 132. Thus, at least one optical test strip 112 or a part thereof may be visible through the window 132 when the color reference card 126 is placed on top of the optical test strip 112. Specifically, at least one reagent test region 114 comprised by the optical test strip 112 may be visible through the window 132 of the color reference card 126. As another example, the color reference card 126 may comprise an optical test strip 112 having a reagent test region 114, specifically in such a way that the reagent test region 112 is accessible and visible. Specifically, the optical test strip 112 may be attached to the color reference card 126 in such a way that the reagent test region 114 is accessible and visible. In such way, the color reference card 126 and the reagent test region 114 may both be in a field of view of a mobile device 122 for capturing an image comprising at least a part of the reagent test region 114 and at least a part of at least one color reference field 128 of the color reference card 126.

[0190] Further, the color reference card 126 may comprise at least one marker 134. The marker 134 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. The marker 134 may be arranged in at least one corner 136 of the color reference card 126. For example, at least one marker 134 may be arranged in each of the corners 136 of the color reference card 126, specifically in such a way that the marker 134 may be visible together with the plurality of color reference fields 128. Further, the marker 134 may comprise information about an orientation of the color reference card 126. For further details relating to the color reference card 126, reference may also be made to international publication number WO 2021/228730 A1.

[0191] The determination system 110 further comprises at least one processor 138. As an example, the at least one processor 138 may at least partially be comprised by at least one computer 140. Additionally or alternatively, the at least one processor 138 may at least partially be comprised by at least one mobile device 122. The at least one processor 138 may be cloud based. Thus, the at least one processor 138 may, as an example, be distributed over at least one computer 140 and/or at least one mobile device 122. The at least one computer 140 and/or the at least one mobile device may at least partially be interconnected, such as by at least one connection 142. The at least one connection 142 may be wire bound and/or wireless. As an example, the at least one computer 140 may be designated for evaluating images captured by the mobile devices 122. Thus, as an example, the at least one computer 140 may be connected to the mobile devices 122 by connections 142, specifically for retrieving images from the mobile devices 122. The processor 138, specifically when at least partially comprised by at least one mobile device 122, may be configured for supporting capturing of at least one image. As an example, the processor 138 may prompt a user of the mobile device 122 to capture the image. Additionally or alternatively, the processor 138 may be configured for automatically capturing the image, e.g., when a reagent test region 114 and/or the color reference card 126 may be in a field of view.

[0192] The processor 138 is configured for retrieving a training set of images. The training set of images comprises images captured with the camera 124. Each image of the training set of images comprises at least a part of a reagent test region 114 of an optical test strip 112 of the training set of optical test strips 112 and at least a part of at least one color reference field 128 of the color reference card 126. Specifically, as indicated in FIG. 1, an image of an entire color reference card 126 having an optical test strip 112 attached such that a reagent test region 114 of the optical test strip 112 is visible through a window 132 of the color reference card 126 may be captured by using a mobile device 122. Thus, each image of the training set of images may specifically comprise an entire a reagent test region 114 and an entire color reference card 126.

[0193] The processor 138 is further configured for determining, for at least one color channel of the cameras 124 of the mobile devices 122 of the training set 121 of mobile devices 122, a training set of pairs of reagent test region coefficients of variation (Cv.sub.TR) and corresponding minimum color reference field coefficients of variation (Cv.sub.RF, min). Each reagent test region coefficient of variation (Cv.sub.TR) is determined by measuring a color variation within the reagent test region 114. Each color reference field coefficient of variation (Cv.sub.RF) is determined by measuring a color variation within the color reference field 128. A minimum color reference field coefficient of variation (Cv.sub.RF, min) for the corresponding reagent test region coefficient of variation (Cv.sub.TR) is determined by comparing the color reference field coefficients of variation (Cv.sub.RF) of the color reference fields 128 of which a common image was captured together with the corresponding reagent test region 114. Specifically, as indicated in FIG. 1, an image of an entire color reference card 126 having an optical test strip 112 attached such that a reagent test region 114 of the optical test strip 112 is visible through a window 132 of the color reference card 126 may be captured by using a mobile device 122. In this case, a minimum color reference field coefficient of variation (Cv.sub.RF, min) may specifically be determined for the entire color reference card 126.

[0194] The processor 138 is further configured for deriving, from the training set of pairs of reagent test region coefficients of variation (Cv.sub.TR) and corresponding minimum color reference field coefficients of variation (Cv.sub.RF, min), a relation for determining the dynamic coefficient of variation limit (Cv.sub.TR, lim) for the respective reagent test region by using the corresponding measured minimum color reference field coefficient of variation (Cv.sub.RF, min). The dynamic coefficient of variation limit (Cv.sub.TR, lim) defines a maximum coefficient of variation (Cv.sub.TR, max) for reagent test regions 114 of non-corrupted optical test strips 116. The determination system 110 may specifically be configured for being used in the determination method according to any one of the embodiments disclosed above or below in further detail referring to a determination method, specifically for performing at least steps e) and f) of the determination method according to any one of the embodiments disclosed above or below in further detail referring to a determination method.

[0195] FIG. 2 schematically shows an exemplary embodiment of a mobile device 122 as proposed herein. The mobile devices 122 has at least one processor 138. The mobile device 122 is configured for performing at least steps iv) to x) of the measurement method according to any one of the embodiments disclosed above or below in further detail referring to a measurement method. The mobile device 122 for performing the measurement method typically is not identical to any one of the mobile devices 122 of the training set of mobile devices of the determination system 110. However, the mobile device 122 for performing the measurement, such as the mobile device 122 depicted in FIG. 2, may, as an example, be of the same type as at least one of the mobile devices 122 of the training set 121 of mobile devices 122 depicted in FIG. 1. The mobile device 122 depicted in FIG. 2 may, however, also be identical to one of the mobile devices 122 of the training set 121 of mobile devices 122 depicted in FIG. 1. Additionally or alternatively, the mobile device 122 depicted in FIG. 2 may be of a specific type not being amongst the one or more types of mobile devices 122 of the training set 121 of mobile devices 122 depicted in FIG. 1.

[0196] FIG. 3 shows a flow chart of an embodiment of a determination method of determining a dynamic coefficient of variation limit (Cv.sub.TR, lim) for assessing validity of an optical test strip 112 usable for an analytical measurement based on a color formation reaction. The determination method comprises the following steps which, as an example, may be performed in the given order. It shall be noted, however, that a different order may generally also be possible. Further, it may also be possible to perform one or more of the method steps once or repeatedly. Further, it may be possible to perform two or more of the method steps simultaneously or in a timely overlapping fashion. The determination method may comprise further method steps which are not listed.

[0197] The determination method comprises: [0198] a) (denoted with reference number 144) providing a training set 111 of optical test strips 112, each optical test strip 112 having a reagent test region 114, wherein at least two of the optical test strips 112 are non-corrupted and wherein at least two of the optical test strips 112 are corrupted; [0199] b) (denoted with reference number 146) providing a training set 121 of mobile devices 122, each mobile device 122 having at least one camera 124; [0200] c) (denote with reference sign 148) providing at least one color reference card 126 having a plurality of color reference fields 128 having known reference color values; [0201] d) (denoted with reference number 150) capturing, by using the mobile devices 122 of the training set 121 of mobile devices 122, a training set of images, wherein each image of the training set of images comprises at least a part of at least one reagent test region 114 of an optical test strip 112 of the training set 111 of optical test strips 112 and at least a part of at least one color reference field 128 of the color reference card 126; [0202] e) (denoted with reference number 152) determining, specifically by using at least one processor 138, more specifically at least one processor 138 of the mobile device 122, for at least one color channel of the cameras 124 of the mobile devices 122 of the training set 121 of mobile devices 122, a training set of pairs of reagent test region coefficients of variation (Cv.sub.TR) and corresponding minimum color reference field coefficients of variation (Cv.sub.RF, min), wherein each reagent test region coefficient of variation (Cv.sub.TR) is determined by measuring a color variation within the reagent test region 114, wherein each color reference field coefficient of variation (Cv.sub.RF) is determined by measuring a color variation within the color reference field 128, wherein a minimum color reference field coefficient of variation (Cv.sub.RF, min) for the corresponding reagent test region coefficient of variation (Cv.sub.TR) is determined by comparing the color reference field coefficients of variation (Cv.sub.RF) of the color reference fields 128 of which a common image was captured together with the corresponding reagent test region 114; [0203] f) (denoted with reference number 154) deriving, from the training set of pairs of reagent test region coefficients of variation (Cv.sub.TR) and corresponding minimum color reference field coefficients of variation (Cv.sub.RF, min), a relation for determining the dynamic coefficient of variation limit (Cv.sub.TR, lim) for the respective reagent test region 114 by using the corresponding measured minimum color reference field coefficient of variation (Cv.sub.RF, min), wherein the dynamic coefficient of variation limit (Cv.sub.TR, lim) defines a maximum coefficient of variation (Cv.sub.TR, max) for reagent test regions 113 of non-corrupted optical test strips 116.

[0204] The determination method may further comprise step g) (denoted with reference number 156) of applying a sample of bodily fluid to the reagent test region 114 of the optical test strip 112. Step g) may specifically be performed before step d). The determination method may further comprise step h) (denoted with reference number 158) of attaching at least one optical test strip 112 of the training set 111 of optical test strips 112 to the color reference card 126 comprising a plurality of color reference fields 128 having known reference color values. Step h) may be performed before step d) and optionally before step g).

[0205] Step e) may further comprise labelling the pairs of reagent test region coefficients of variation (Cv.sub.TR) and corresponding minimum color reference field coefficients of variation (Cv.sub.RF, min) of the training set of pairs of reagent test region coefficients of variation (Cv.sub.TR) and corresponding minimum color reference field coefficients of variation (Cv.sub.RF, min) with information on whether the respective optical test strip 112 of the training set 111 of optical test strips 112 was corrupted or non-corrupted. The labelling may specifically be taken into consideration in step f). In step f), the dynamic coefficient of variation limit (Cv.sub.TR, lim) may exclude at least 90%, specifically at least 95%, more specifically at least 99%, of the corrupted optical test strips 118 of the training set 111 of optical test strips 112. In step f), the dynamic coefficient of variation limit (Cv.sub.TR, lim) may permit acceptance of at least 80%, specifically at least 90%, more specifically at least 95%, more specifically at least 97%, more specifically at least 99%, of the non-corrupted optical test strips 116 of the training set 111 of optical test strips 112. In other words, in step f), the dynamic coefficient of variation limit (Cv.sub.TR, lim) may not exclude more than 5%, specifically more than 3%, more specifically more than 1%, of the non-corrupted optical test strips 116 of the training set 111 of optical test strips 112. The relation derived in step f) may comprise at least one of a look-up table, a model, an algorithm and a function. The relation derived in step f) may comprise a function. The function may be a linear function. The linear function may have a slope of 1.

[0206] The dynamic coefficient of variation limit (Cv.sub.TR, lim) may comprise a predefined maximum coefficient of variation limit (Cv.sub.TR, max, predefined) for reagent test regions 114 which is not exceedable. Step f) may comprise using at least one machine-learning algorithm, specifically by training a trainable model by using the training set of pairs of reagent test region coefficients of variation (Cv.sub.TR) and corresponding minimum color reference field coefficients of variation (Cv.sub.RF, min). In step e), the pairs of reagent test region coefficients of variation (Cv.sub.TR) and corresponding minimum color reference field coefficients of variation (Cv.sub.RF, min) may be determined for at least two color channels, specifically for at least two color channels selected from the group consisting of: a green color channel, a blue color channel and a red color channel. In step f), the dynamic coefficient of variation limit (Cv.sub.TR, lim) may be derived for the at least two color channels for which the pairs of reagent test region coefficients of variation (Cv.sub.TR) and corresponding minimum color reference field coefficients of variation (Cv.sub.RF, min) may be determined in step e). As an example, for each color channel an individual dynamic coefficient of variation limit (Cv.sub.TR, lim) may at first be derived, wherein the individual dynamic coefficient of variation limits (Cv.sub.TR, lim) may subsequently be compared with each other.

[0207] However, specifically, for each color channel, an individual dynamic coefficient of variation limit (Cv.sub.TR, lim) may be derived, wherein, for each color channel, the reagent test region coefficient of variation (Cv.sub.TR) may be compared to the individual dynamic coefficient of variation limit (Cv.sub.TR, lim) of the color channel, wherein, for a non-corrupted optical test strip 116, the reagent test region coefficients of variation (Cv.sub.TR) may have to be smaller than, or optionally equal to, the individual dynamic coefficient of variation limit (Cv.sub.TR, lim) of the color channel for all color channels. In other words, for a corrupted optical test strip 118, the reagent test region coefficients of variation (Cv.sub.TR) may have to be larger than, or optionally equal to, the individual dynamic coefficient of variation limit (Cv.sub.TR, lim) of at least one color channel. As an example, the green color channel and the red color channel may be considered. Then, as an example, for a non-corrupted optical test strip 116, the coefficient of variation (Cv.sub.TR) of the green color channel may have to be smaller than, or optionally equal to, the individual dynamic coefficient of variation limit (Cv.sub.TR, lim) of the green color channel and the coefficient of variation (Cv.sub.TR) of the red color channel may have to be smaller than, or optionally equal to, the individual dynamic coefficient of variation limit (Cv.sub.TR, lim) of the red color channel. In other words, for a corrupted optical test strip 118, the coefficient of variation (Cv.sub.TR) of the green color channel may have to be larger than, or optionally equal to, the individual dynamic coefficient of variation limit (Cv.sub.TR, lim) of the green color channel or the coefficient of variation (Cv.sub.TR) of the red color channel may have to be larger than, or optionally equal to, the individual dynamic coefficient of variation limit (Cv.sub.TR, lim) of the red color channel. Further options are also feasible.

[0208] FIG. 4 shows experimental data referring to an embodiment of a determination method according to this disclosure. Specifically, FIG. 4 graphically illustrates pairs of reagent test region coefficients of variation (Cv.sub.TR) and corresponding minimum color reference field coefficients of variation (Cv.sub.RF, min) used for deriving a relation for determining the dynamic coefficient of variation limit (Cv.sub.TR, lim) by using a measured minimum color reference field coefficient of variation (Cv.sub.RF, min). As said, the relation may be a function, specifically a linear function, which is the case here. In FIG. 4, measured reagent test region coefficients of variation (Cv.sub.TR) are plotted against measured corresponding minimum color reference field coefficients of variation (Cv.sub.RF, min). Specifically, a color reference card 126 comprising 20 color reference field 128 was used for this purpose, wherein, by using different mobile devices 122 of a training set 121 of mobile devices 122, a training set of images was captured, each image comprising the entire color reference card 126 together with different reagent test regions 114 of different optical test strips 112 of a training set 111 of optical test strips 112. FIG. 4 specifically indicates three clouds of data points which may specifically, at least partially, refer to different mobile devices 122 of the training set 121 of mobile devices 122, more specifically to different types of mobile devices 122 of the training set 121 of mobile devices 122 such as different smart phones types. The optical test strips 112 used for the experiments shown in FIG. 4 were labelled as either corrupted or non-corrupted. Data referring to non-corrupted optical test strips 116 are indicated by dots in FIG. 4. Crosses indicate data referring to corrupted optical test strips 118 or to data referring to non-corrupted optical test strips 116 in FIG. 4. Specifically, the crosses may refer to so called provocation experiments which may comprise using non-corrupted optical test strips 116 or corrupted optical test strips 118. Thus, for one provocation experiment either a non-corrupted optical test strip 116 or a corrupted optical test strip 118 may be used. The provocation experiments may mainly use corrupted optical test strips 118. Specifically, at least 70% of the provocation experiments may use corrupted optical test strips 118, more specifically, at least 80% of the provocation experiments may use corrupted optical test strips 118, most specifically at least 90% of the provocation experiments may use corrupted optical test strips 118. Thus, at least some of the crosses shown in FIG. 4, specifically crosses below a derived dynamic coefficient of variation limit (Cv.sub.TR, lim), may in fact refer to non-corrupted optical test strips 116. Based on this data, the following relation for the dynamic coefficient of variation limit (Cv.sub.TR, lim) was derived:

[00002]$C{v}_{\mathrm{TR},\lim }=C{v}_{\mathrm{RF},\min }+0.045.$

[0209] The dynamic coefficient of variation limit (Cv.sub.TR, lim) is plotted as geometrical line denoted with reference number 160 in FIG. 4. Further, a range above the geometrical line 160 is denoted with reference number 159 and a range below the geometrical line 160 is denoted with reference number 161 in FIG. 4. Thus, the dynamic coefficient of variation limit (Cv.sub.TR, lim) in form of the geometrical line 160 separates the range 159 from the range 161. With respect to a later use for a measurement method of performing an analytical measurement, the range 159 may specifically refer to optical test strips 112 invalid for analytical measurements and the range 161 may specifically refer to optical test strips 112 valid for analytical measurements. As can be seen, the determined dynamic coefficient of variation limit (Cv.sub.TR, lim) excludes a large extent of data points which may refer to corrupted optical test strips 118 (indicated by crosses in FIG. 4), while specifically allowing all data points which certainly refer to non-corrupted optical test strips 116 (indicated by dots in FIG. 4). Thus, the determined dynamic coefficient of variation limit (Cv.sub.TR, lim) can be well used for identifying corrupted optical test strips 118 and for assessing validity of an optical test strip 112 for analytical measurements.

[0210] FIG. 5 shows a flow chart of an embodiment of a measurement of performing an analytical measurement based on a color formation reaction by using a mobile device 122 having a camera 124 and a processor 138. The measurement method comprises the following steps which, as an example, may be performed in the given order. It shall be noted, however, that a different order may generally also be possible. Further, it may also be possible to perform one or more of the method steps once or repeatedly. Further, it may be possible to perform two or more of the method steps simultaneously or in a timely overlapping fashion. The measurement method may comprise further method steps which are not listed.

[0211] The measurement method comprises: [0212] i) (denoted with reference number 162) providing at least one optical test strip 112 having at least one reagent test region 114, wherein the optical test strip 112 specifically is of the same type of optical test strips 112 as the optical test strips 112 of the training set used in step a) of the determination method according to any one of the embodiments described above or below in further detail referring to a determination method; [0213] ii) (denoted with reference number 164) providing at least one color reference card 126 having a plurality of color reference fields 128 having known reference color values; [0214] iii) (denoted with reference number 166) capturing, by using the camera 124, at least one image of at least a part of the reagent test region 114 having at least one sample of at least one bodily fluid applied thereto and at least a part of at least one of the color reference fields 128 of the color reference card 126; [0215] iv) (denoted with reference number 168) determining, specifically by using the processor 138, for at least one color channel of the camera 124 of the mobile device 122, a color reference field coefficient of variation (Cv.sub.RF) for at least one of the color reference fields 128 by using the image, wherein the color reference field coefficient of variation (Cv.sub.RF) is determined by measuring a color variation within the at least one color reference field 128; [0216] v) (denoted with reference number 170) determining, specifically by using the processor 138, a minimum color reference field coefficient of variation (Cv.sub.RF, min) for the color reference card 126 by using the at least one color reference field coefficient of variation (Cv.sub.RF) determined in step iv); [0217] vi) (denoted with reference number 172) determining, specifically by using the processor 138, a dynamic coefficient of variation limit (Cv.sub.TR, lim) for the reagent test region 114 by using the minimum color reference field coefficient of variation (Cv.sub.RF, min) determined in step v) and by using a relation for determining the dynamic coefficient of variation limit (Cv.sub.TR, lim), wherein the relation is determined by performing the determination method according to any one of the embodiments described above or below in further detail referring to a determination method; [0218] vii) (denoted with reference number 174) determining, specifically by using the processor 138, for the at least one color channel, a reagent test region coefficient of variation (Cv.sub.TR) of the reagent test region 114 by using the image, wherein the reagent test region coefficient of variation (Cv.sub.TR) is determined by measuring a color variation within the reagent test region 114; [0219] viii) (denoted with reference number 176) comparing, for the at least one color channel, the reagent test region coefficient of variation (Cv.sub.TR) to the determined dynamic coefficient of variation limit (Cv.sub.TR, lim) for the reagent test region 114; [0220] ix) (denoted with reference number 178) if the reagent test region coefficient of variation (Cv.sub.TR) is larger than the dynamic coefficient of variation limit (Cv.sub.TR, lim), considering the optical test strip 112 to be corrupted and aborting the measurement method; and [0221] x) (denoted with reference number 180) if the reagent test region coefficient of variation (Cv.sub.TR) is smaller than the dynamic coefficient of variation limit (Cv.sub.TR, lim), considering the optical test strip 112 to be non-corrupted and determining a concentration of at least one analyte in the sample of bodily fluid by using, for the at least one color channel, at least one color formation value for a color formation of the reagent test region 114 having at least one sample of at least one bodily fluid applied to the reagent test region 114 of the optical test strip 112.

[0222] As indicated above in the context of the determination method, the dynamic coefficient of variation limit (Cv.sub.TR, lim) separates possible reagent test region coefficients of variation (Cv.sub.TR) into two possible cases: Firstly, the range 161 below the dynamic coefficient of variation limit (Cv.sub.TR, lim) in FIG. 4, i.e., below the geometrical line 160, denoting optical test strips 112 validly usable for the measurement method of performing the analytical measurement and, secondly, the range 159 above the dynamic coefficient of variation limit (Cv.sub.TR, lim) in FIG. 4, i.e., above the geometrical line 160, denoting optical test strips 112 not validly usable for the measurement method of performing the analytical measurement. The dynamic coefficient of variation limit (Cv.sub.TR, lim) in FIG. 4, i.e., the geometrical line 160, itself, may be counted as being part of range 159, as being part of range 161, or none. Thus, generally, steps ix) and x) of the method as described imply checking in which of ranges 159 and 161 the test strip 112 intended for the actual run of the measurement method actually is located, thereby deciding if the test strip 112 actually may be validly used, e.g., being corrupted or not, and, depending on said decision, taking the appropriate further steps as listed in steps ix) and x).

[0223] The measurement method may further comprise at least one step of applying the at least one sample of the at least one bodily fluid to the reagent test region 114 of the optical test strip 112, wherein the measurement method is performed according to one of the following ways: [0224] the dynamic coefficient of variation limit (Cv.sub.TR, lim) in step vi) is determined by using a relation derived when performing the determination method according to any one of the embodiments disclosed above or below in further detail referring to a determination method having at least one sample of the at least one bodily fluid applied to the reagent test regions 114 of the optical test strips 112 of the training set 111 of optical test strips 112, wherein the measurement method comprises applying the sample of the bodily fluid to the reagent test region 114 of the optical test strip 112 before performing step iii); or [0225] the dynamic coefficient of variation limit (Cv.sub.TR, lim) in step vi) is determined by using a relation derived when performing the determination method according to any one of the embodiments disclosed above or below in further detail referring to a determination method having no sample of the at least one bodily fluid applied to the reagent test regions 114 of the optical test strips 112 of the training set 111 of optical test strips 112, wherein the measurement method comprises performing steps iii) to viii) with no sample of the at least one bodily fluid applied to the reagent test region 114 of the optical test strip 112, and wherein the method further comprises applying the at least one sample of the bodily fluid to the reagent test region 114 of the optical test strip 112 before or during performing step x).

[0226] The measurement method may further comprise step xi) (denoted by reference number 182) of attaching the optical test strip to the color reference card. Step xi) may be performed before step iii).

[0227] FIG. 6 shows experimental data referring to an embodiment of a measurement method according to this disclosure. Specifically, FIG. 6 show a consensus error grid, also referred to as Parkes error grid, which is a tool for evaluating an accuracy of blood glucose measurements. For further details regarding consensus error grids, reference may be made to Journal of Diabetes Science and Technology, Volume 7, Issue 5, September 2013 Diabetes Technology Society, Technical Aspects of the Parkes Error Grid, Andreas Pfiitzner, M.D., Ph.D., David C. Klonoff, M.D., Scott Pardo, Ph.D., and Joan L. Parkes, Ph.D. FIG. 6 plots a measured blood glucose (MBG) level against an actual blood glucose (ABG) level of a user, wherein the blood glucose level was measured according to the measurement method of this disclosure. In simplified terms, the consensus error grid shows different standardized zones ranging from a practically non-critical zone A to a highly critical zone E for a user administering insulin depending on a measured blood glucose level. A large discrepancy between a measured blood glucose level and an actual blood glucose level may result in an unsuitable insulin administration and can thus be highly critical and even life threatening for the user. The consensus error grid comprises data obtained by using non-corrupted optical test strips 116 as well as corrupted optical test strips 118. The large circles plotted in the consensus error grid refer to data which could be detected by using a dynamic coefficient of variation limit (Cv.sub.TR, lim) determined according to the above-derived function

[00003]$C{v}_{\mathrm{TR},\lim }=C{v}_{\mathrm{RF},\min }+0.045.$

[0228] Thus, specifically, a plurality of rather critical blood glucose measurements, e.g., in zone C, could be identified and the corresponding measurements could have been aborted in time. Contrarily, a static coefficient of variation limit of 0.09 would have detected only 1 data point.

[0229] 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 p pertains and which fall within the limits of the appended claims.

LIST OF REFERENCE NUMBERS

[0230] 110 determination system [0231] 111 training set of optical test strips [0232] 112 optical test strip [0233] 114 reagent test region [0234] 116 non-corrupted optical test strip [0235] 118 corrupted optical test strip [0236] 120 grid pattern [0237] 121 training set of mobile devices [0238] 122 mobile device [0239] 124 Camera [0240] 126 color reference card [0241] 128 color reference field [0242] 130 gray color reference field [0243] 132 Window [0244] 134 marker [0245] 136 Corner [0246] 138 Processor [0247] 140 Computer [0248] 142 Connection [0249] 144 determination method step a) [0250] 146 determination method step b) [0251] 148 determination method step c) [0252] 150 determination method step d) [0253] 152 determination method step e) [0254] 154 determination method step f) [0255] 156 determination method step g) [0256] 158 determination method step h) [0257] 159 range above geometrical line [0258] 160 geometrical line [0259] 161 range below geometrical line [0260] 162 measurement method step i) [0261] 164 measurement method step ii) [0262] 166 measurement method step iii) [0263] 168 measurement method step iv) [0264] 170 measurement method step v) [0265] 172 measurement method step vi) [0266] 174 measurement method step vii) [0267] 176 measurement method step viii) [0268] 178 measurement method step ix) [0269] 180 measurement method step x) [0270] 182 measurement method step xi)