Impact of color blindness on recognition of blood in body fluids

Background: Color blindness is a common hereditary X-linked disorder. Objective: To investigate whether color blindness affects the ability to de tect the presence of blood in body fluids. Methods: Ten color-blind subjects and 20 sex- and age-matched control subje cts were shown 94 photographs of stool, urine, or sputum. Frank blood was p resent in 57 (61%) of the photographs. Surveys were done to determine if bo ard-certified internists had ever considered whether color blindness would affect detection of blood and whether an inquiry on color blindness was inc luded in their standard medical interview. Results: Color-blind subjects were significantly less able to identify corr ectly whether pictures of body fluids showed blood compared with non-color- blind controls (P = .001); the lowest rate of correct identifications occur red with pictures of stool (median of 26 [70%] of 37 for color-blind subjec ts vs 36.5 [99%] of 37 for controls; P<.001). The more severely color-blind subjects were significantly less accurate than those with less severe colo r deficiency (P = .009). Only 2 (10%) of the 21 physicians had ever conside red the possibility that color blindness might affect the ability of patien ts to detect blood, and none routinely asked their patients about color bli ndness. Conclusions: Color blindness impairs recognition of blood in body fluids. C olor-blind individuals and their health care providers need to be made awar e of this limitation.