The present invention provides an agglutination based assay system for determining the presence and/or amount of analyte in a sample comprising a test device having one or more capillary pathways comprising detection regions adapted for non-visual detection of a sample which is releasably engageable with a reader which comprises detection means for detecting the sample at the detection regions in each of said capillary pathways and electronic means for indicating the presence and/or amount of analyte.