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 normal yellow color is due to urochrome, a pigment metabolite arising from the body's destruction of hemoglobin.n fact, this has come from the break down of the better known pigment found in blood, haemoglobin. Basically It's due to excretion of urochrome, a blood pigment. Urochrome is a yellow-colored pigment that gives the color to urine.