Drug companies and diagnostic test developers are increasingly teaming up to produce theranostics, a treatment strategy that packs a one-two punch: a diagnostic test that identifies patients most likely to be helped or harmed by a new medication, and targeted drug therapy based on the test results. Theranostic tests differ from traditional ones such as those for blood glucose, because the new tests are based on sophisticated technology involving genetics, molecular biology, and testing platforms such as microchips. The test results are used to tailor treatment, usually with a drug that targets a particular gene or protein.