The ELISA (enzyme-linked immunosorbent assay) is a test which uses color change and antibodies to identify a substance. An indirect ELISA is one of three ELISA tests.
Urine varies in appearance, depending principally upon a body's level of hydration, as well as other factors. Normal urine is a transparent solution ranging from colorless to amber but is usually a pale yellow. In the urine of a healthy individual the color comes primarily from the presence of urobilin.
Normal urine varies in color from almost colorless to dark yellow. Some foods, such as beets and blackberries, may turn urine red. Usually, glucose, ketones, protein, and bilirubin are not detectable in urine.