Blood test cassette. Cassette used to test blood for specific substances, such as antibodies to certain infections, or levels of certain hormones. A drop of blood is placed in the sample well (S), along with several drops of diluent. After a short time, the blood moves up the test strip within the cassette and passes through the test line (T) and the control line (C). The test line is impregnated with a reactant and will form a visible line if the substance being tested for is present in the blood in sufficient concentration. The control line is for comparison. If no test line appears, the result is negative. This cassette shows a positive result for HIV-1/HIV-2 (human immunodeficiency virus) antibody, indicating the subject has the HIV virus which causes AIDS (acquired immune deficiency syndrome).