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.
Dark Yellow Urine Causes. The natural color of urine is pale yellow, however, it can become dark yellow, brown, or reddish in color, due to a number of factors like dehydration, and the intake of certain foods and medications.ark Yellow Urine Causes. The natural color of urine is pale yellow, however, it can become dark yellow, brown, or reddish in color, due to a number of factors like dehydration, and the intake of certain foods and medications.