Abstract: An assay device is disclosed comprising a housing and a test portion, electronic circuitry and a one-piece optical component each a least partially located in the housing. The test portion comprises one or more test zones adapted to receive an analyte and a fluorescent label associated with the analyte, the fluorescent label being excitable by excitation light and adapted to emit emission light upon excitation by excitation light. The electronic circuitry comprises one or more light sources and one or more light detectors. The optical component comprises one or more excitation light guides adapted to guide excitation light from the one or more light sources to the one or more test zones, and one or more emission light guides adapted to guide emission light from the one or more test zone to the one or more light detectors.