Abstract: An analytical test device for competition assay for particular non-protein antigens, such as antigens representing drugs of abuse, is disclosed. The analytical test device is a test kit housing having an opening for introduction of a body fluid sample and a flow path for the body fluid sample. A supply of microscopic colored latex particles is adjacent to the opening along the flow path. A chromatographic membrane support is within the test kit housing for exposing the colored latex particles to the body fluid sample. When non-protein antigens are not present in the body fluid specimen, the colored latex particles accumulate at a predetermined site on the chromatographic membrane by complexing of antibodies on the colored latex particles to a drug conjugate probe on the membrane support to leave a visually perceptible colored mark of the same color as the colored latex particles.