The product profile for Ictotest® points out that bilirubin is very light sensitive, so urine specimens should be protected from excessive light exposure and examined as quickly as possible when received in the laboratory. On standing, bilirubin, which has a goldish color, is oxidized to biliverdin, which is a green color. Many of the procedures used to detect bilirubin will not react with biliverdin, so false-negative results may occur if urine is not fresh when tested.