Abbreviated “ChLIA,” this is a testing method used in blood donor infectious disease screening. ChLIA is very similar in concept to enzyme immunoassay (EIA) in both bind a substance (antigen or antibody) through use of a capture reagent attached to a microwell plate (for example) and detect that substance by a secondary method. EIA uses an enzyme attached to the detecting antibody or antigen; that enzyme catalyzes a reaction that typically gives a visible color change indicating that the substance of interest is present. ChLIA, on the other hand, does not use an enzyme but rather a substance that actually reacts to emit visible light to indicate a positive reaction (a familiar example of chemiluminescence is the “crack and glow” lightstick that my kids enjoyed when they were younger and pretty much everyone has seen). ChLIA is approved by the U.S. FDA for use in tests from certain manufacturers for anti-HBc, anti-HCV, anti-HIV 1,2, HBsAg, and anti-T. cruzi.