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.
the fluid secreted by the kidneys, transported by the ureters, stored in the bladder, and voided through the urethra. Normal urine is clear, straw-colored, and slightly acid; has the odor of urea; and has a specific gravity between 1.003 and 1.035. Its normal constituents include water, urea, sodium chloride, potassium chloride, phosphates, uric acid, organic salts, and the pigment urobilin.