When her hairdresser asked her last fall whether she would continue wearing her hair long, Elizabeth Sloan broke down crying. Unbeknown to the hairstylist, Ms. Sloan had recently had a breast tumor removed and was expecting to begin chemotherapy, which would probably mean losing her hair. But later that day, Ms. Sloan received the results of a new $3,500 genetic test, which indicated that her cancer probably would not come back even if she skipped chemotherapy. ‘It was a huge relief,’ said Ms. Sloan, 40, a mother of two young boys who lives in Manhattan. ‘I did not want to napalm-bomb my body with chemicals.’ The test taken by Ms. Sloan, known as Oncotype DX and offered by a company called Genomic Health, is part of a new wave of sophisticated genetic or protein tests that are starting to remake the diagnostics business, both for the technology they use and the way they are developed and sold. Traditionally regarded as a low-profit, poor cousin of prescription drugs, diagnostic tests are emerging as high-profit products in their own right. Test developers are ‘trying to do what pharmaceutical companies have done with their drugs,’ said Jondavid Klipp, managing […]