Abstract: A test device for assaying liquid samples for the presence of a predetermined reagent is described. The device comprises telescoping top and bottom members defining a liquid reservoir therebetween, resilient means for biasing the members in the open position, one or more test wells in the top member with bottom openings covered with microporous membranes, a co-reactant immobilized on the membrane surfaces, and sorbent means between the members spaced from the membrane(s) in the open position but in contact therewith in the closed position. Liquids are passed through the membrane(s) into the sorbent means by depressing the members to the closed position.