Low-cost assay test strip readers enable creation of profiles of analyte reactions detected on an assay test strip utilizing a simple detector fixedly mounted to a body of the reader. The detector may be a single detector, such as a photodetector, which detects an optical signal at a single point. The assay test strip is inserted and/or removed from the test strip reader and the detector detects the optical elements of the strip during such insertion and/or removal. The movement of the test strip with respect to the body enables the detector to scan a length of the test strip, thereby generating a profile of optical signals representing analyte reactions along a one-dimensional portion of the test strip. The reader may convert the detected profile into a displayable indication of analyte concentrations for diagnostic purposes.