Assay devices and methods

A lateral flow device for determining an assay result, comprising:

• a test strip comprising at least an upstream first zone and a second zone downstream from the first zone, wherein the upstream first zone is a test zone and the downstream second zone is a control or reference zone, said first zone and second zone are discrete and spaced apart such that a fluid front flows from the first zone to the second zone along a lateral flow path defined by the test strip;
• a light source system configured to illuminate the first zone and the second zone of the test strip;
• a photodetector configured to detect light from the first and the second zones when each respective zone is illuminated by the light source and output a first signal from the first zone and a second signal from the second zone;
• and
• a processor configured to receive and process the first and second signals and generate a processed value, compare the processed value to a threshold, and generate an output signal if the processed value exceeds the threshold, the output signal indicative of a positive result if the processed value exceeds the threshold,
• wherein the processor is configured to amend the first signal at the test zone based on the second signal at the control or reference zone.