A portable rapid diagnostic test reader system comprising: a mobile phone or other portable electronic device having a camera and one or more processors contained therein, the mobile phone or other portable electronic device containing imaging software thereon executable by the one or more processors; a modular housing configured to mount to the mobile phone or other electronic device, the modular housing including a receptacle configured to receive a sample tray holding a rapid diagnostic test, the rapid diagnostic test comprising a test location and control location; at least one illumination source (60, 62) arranged to pass light to the test location and control location, said at least one illumination source (60, 62) being disposed in the modular housing and located on one side of the rapid diagnostic test; an optical demagnifier disposed in the modular housing and positioned adjacent to the camera, the optical demagnifier arranged to demagnify the image of the rapid diagnostic test to place the test location and control location in a field of view of the camera; and wherein the imaging software is adapted to extract regions of interest from the test location and the control location in an image of the field of view and is adapted to compare respective regions of interest with respective threshold values and is further adapted to characterize the rapid diagnostic test, the system being characterized in that it comprises a removable color filter interposed between the camera and the optical demagnifier; and in that the at least one illumination source (60, 62) comprises: - a first illumination source arranged to pass light to the test location and control location, said first illumination source being disposed in the modular housing and located on a first side of the rapid diagnostic test, - a second illumination source arranged to pass light to the test location and control location, said second illumination source being disposed in the modular housing and located at a second, opposing side of the rapid diagnostic test, and - a switch to selectively illuminate the rapid diagnostic test with either the first illumination source or the second illumination source. a mobile phone or other portable electronic device having a camera and one or more processors contained therein, the mobile phone or other portable electronic device containing imaging software thereon executable by the one or more processors; a modular housing configured to mount to the mobile phone or other electronic device, the modular housing including a receptacle configured to receive a sample tray holding a rapid diagnostic test, the rapid diagnostic test comprising a test location and control location; at least one illumination source (60, 62) arranged to pass light to the test location and control location, said at least one illumination source (60, 62) being disposed in the modular housing and located on one side of the rapid diagnostic test; an optical demagnifier disposed in the modular housing and positioned adjacent to the camera, the optical demagnifier arranged to demagnify the image of the rapid diagnostic test to place the test location and control location in a field of view of the camera; and wherein the imaging software is adapted to extract regions of interest from the test location and the control location in an image of the field of view and is adapted to compare respective regions of interest with respective threshold values and is further adapted to characterize the rapid diagnostic test, the system being characterized in that it comprises a removable color filter interposed between the camera and the optical demagnifier; and in that the at least one illumination source (60, 62) comprises: - a first illumination source arranged to pass light to the test location and control location, said first illumination source being disposed in the modular housing and located on a first side of the rapid diagnostic test, - a second illumination source arranged to pass light to the test location and control location, said second illumination source being disposed in the modular housing and located at a second, opposing side of the rapid diagnostic test, and - a switch to selectively illuminate the rapid diagnostic test with either the first illumination source or the second illumination source. - a first illumination source arranged to pass light to the test location and control location, said first illumination source being disposed in the modular housing and located on a first side of the rapid diagnostic test, - a second illumination source arranged to pass light to the test location and control location, said second illumination source being disposed in the modular housing and located at a second, opposing side of the rapid diagnostic test, and - a switch to selectively illuminate the rapid diagnostic test with either the first illumination source or the second illumination source.