Bilirubin is a very unstable compound. Improper specimen storage can result in false negative bilirubin tests. Bilirubin rapidly photo-oxidizes to biliverdin or hydrolyzes to free bilirubin when exposed to light. Since conjugated bilirubin is the substance detected on the strip pad, neither of these compounds will produce a positive test. Thus, this conversion produces false negatives. Bilirubin's light sensitivity is also temperature dependent. It is enhanced at room temperature and decreased at low and refrigerator temperatures.