A spongy swab is mounted against the distal face of a piston at the end of a push rod. Once humected with a sample fluid, the swab and piston assembly is inserted into a tubular body like the plunger of a syringe. As the swab is pushed and squeezed against the distal end of the body up to a trippable stop, part of the fluid is excreted into a chromatographic immunoassay testing device through a first aperture in a distal section of the body. The remainder of the sample is kept in a sealed chamber between the piston and the end wall of the tubular body until it is excreted through a second aperture for a secondary test by pushing the piston beyond the trippable stop. That preserves the sample within the spongy swab that has been used to collect it; thus preventing the adsorption of the analytes on the surface of a reservoir, and to provide a convenient and rapid way to extract the remainder of the specimen.