An assay test device comprises a cup container having a detachable top cover that has a volume-reducing internal structure. A pocket shaped and dimensioned to nest a chromatographic test strip cartridge is mounted against a flattened transparent portion of the cup side wall. The cartridge is held in a vertical position with an aperture near the top edge of the cup. A splash shield projects for the brim region of the cup over that aperture preventing any part of the sample fluid poured into the cup from entering the cartridge and contacting the test strips prematurely. When the lid is installed and the cup flipped upside-down, the internally projecting structure raises the level of sample fluid for better access to the cartridge aperture. The structure can be adapted to extend all the way through the inside of the cup to contact its closed bottom. A central cavity in the structure having a open end captures a small volume of fluid and preserves it for later confirmatory analysis. In one embodiment of the invention the central cavity is created by a well secured to the bottom of the cup that is telescopically engage by a cap secured to an undersurface portion of the internally projecting structure.