A sample testing device for testing for the presence of a component of interest in a liquid sample includes: (a) a capillary pathway having an upstream end and a downstream end and incorporating a reagent system capable of causing agglutination with the component; (b) optionally, a control capillary pathway; (c) a sampling region to which the liquid sample is applied and from which the sample is able to enter the upstream ends of the test and control capillaries; (d) a power source; (e) detection arrangements electrically associated with the power source for detecting the presence of liquid at a downstream region of the capillaries; (f) a display operated by the power source for indicating the result of the test; and (g) a signal processor associated with the power source, detection arrangement and display for evaluating the result of the test and providing the result on the display.