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.

A method of performing an analytical measurement includes using a camera of a mobile device to capture a time series of images of at least a part of a medical article. From this, image-derived position information on a relative position of the mobile device and the medical article is derived, thereby generating a first time series of position information. A sensor captures measurement information on the relative position of the mobile device and the medical article. Measurement-derived position information is used to generate a second time series of position information, and the first and second time series of position information are combined to generate an augmented time series of position information. From this, guidance is provided to a user to move the mobile device and the medical article into a relative target position. A mobile device, a kit and a computer program are also disclosed.