An improved qualitative or semi-quantitative diagnostic test for low levels of any analyte, such as hCG, in a biological sample, such as urine. The test comprises of 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 detection process to optimize the detection of a valid fluid front, increase the detection limit without compromising the reliability and accuracy of the test system, and improve the determination of test result validity.