Abstract: A disposable electronic assay device comprising card-like housing containing a sample receptor for receiving a sample of body fluid containing an analyte to be determined, a sample treatment element for reaction with sample fluid components to yield a physically detectable change which correlates with the amount of analyte in the sample, a detector responsive to the physically detectable change for producing an electrical signal which correlates with the amount of analyte in the sample, a signal processor connected to the detector for converting the electrical signal to a digital test result output, and visually readable output means connected to the signal processor for receiving and presenting the test result output. The signal processor can include an analog to digital conversion element for converting an analog reflectance or transmission output signal to a digital reflectance output, processor for converting the digital reflectance or transmission output to a digital test result output.