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.
What vitamins turn urine bright yellow? B2 riboflavin in vitamins can cause a bright yellow color in urine because the body flushes excess B2 through the urine. Urine color also varies depending on what the individual eats and drinks. Beets can turn urine pink or red, and carrots can lend an orange hue.