Fumbled DNA tests, adverse events for breast-cancer patients

More than 2,700 diseases can now be identified through gene testing, compared with fewer than 800 in 2000, according to the government-funded website GeneTests. DNA screening offers the potential to transform medicine by predicting the risk of cancer or other severe diseases years in advance. Yet the very nature of the tests creates the potential for catastrophic error because they're often used to make irreversible decisions, such as terminating a pregnancy or undergoing surgery to prevent cancer.