FOR centuries, doctors have been urging patients to watch out for unhealthy
bleeding鈥攊n their stools, urine or saliva. Blood in these can be a sign of
anything from cancer to tuberculosis, and patients are told to report it
promptly. But what if they suffer from red-green colour blindness, a common
hereditary condition?
Gary Wormser and his colleagues from New York Medical College showed
colour-blind people colour photos of samples with and without blood in them
(Archives of Internal Medicine, vol 161, p 461). The colour-blind
subjects were much worse at recognising blood than people who could distinguish
colours, Wormser found. But out of 21 doctors who were surveyed, none ever asked
their patients if they were colour-blind.