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.
It is probably caused by a plant pigment and does not affect the health of the animal.. Red urine is a descriptive term for the condition where a rabbit's urine varies in color from the normal pale yellow to dark yellow, carrot orange, brown, or bright red. Red urine is not a medical problem.