An improved qualitative or semi-quantitative diagnostic test for measuring low levels of any analyte, such as hCG, in a biological sample, such as urine. The test comprises a test device containing reagents for the detection of the monitored analyte and an electronic reader that measures color development at a detection area of the device. The color development is converted to an electronic or digital signal. Improvements were made to the electronic reader to optimize the coverage of the detection area on the test strip. This improves the detection sensitivity and consistency of the test result while maintaining its reliability and accuracy.