What is the Future of Diagnostic Medicine?

I´m lying on the couch watching TV, thinking about popping an Ambien. I take the little white pill a few nights a week to help me sleep (worried wells are often up at 3 a.m., worrying about one thing or another). Suddenly, though, I´m desperate to stay awake. Charlie Rose is on, and tonight´s guest is surgeon Mehmet Oz, director of the Cardiovascular Institute at Columbia University Medical Center. Rose wants to know about the controversy surrounding full-body CT scans, a procedure central to the aims of personalized medicine-a procedure I´m scheduled to have next week. Hundreds of doctors´ offices now advertise the scans as virtual physicals, offering you peace of mind knowing that your organs have been examined for structural abnormalities. Others warn that the scans also expose people to high levels of radiation. Indeed, one of Oz´s colleagues at Columbia, radiation biologist David Brenner, has shown that having a full-body CT scan in middle age carries a 1 in 1,200 risk that you´ll eventually die from radiation-induced cancer.

Oz is alarmingly nonchalant in his caution. â€Well, you´re scanning the whole body. How do you keep protected?†Rose looks flummoxed. I sit up. â€But the bigger issue is that you uncover problems that aren´t problems . . . and that starts a cascade of evaluations, which in themselves carry risks. You´ll cause cancers, probably as many as you´re going to find.â€

In the week leading up to my scan, I had other mail-in diagnostics to deal with. Aside from using our genes to see what diseases might be in store for us, researchers want to use them to customize treatments. Because drugs act differently in every patient based on his or her genetic makeup, biotech companies are developing tests to identify which drugs will function best in which patients.

Biotech giant Genentech has developed Herceptin, a breast-cancer treatment targeted at the 25 percent of patients who have too many copies of a gene called HER2. Tumor cells that have too many copies of the HER2 gene overproduce a protein that promotes increased cell division and faster growth. Doctors look for the HER2 gene malfunction using two FDA-approved tests, and if they find it, they prescribe Herceptin.

Genelex, a small biotech company in Seattle, and Roche Diagnostics, a global pharmaceutical company, are competing to sell tests that predict whether someone will have a bad or potentially fatal reaction to widely prescribed medicines, such as antidepressants, narcotic pain medications, and beta blockers. About half the U.S. population has gene mutations that either hasten or slow the absorption of these drugs into the body, mutations that can create adverse reactions.

Genelex sent me a test tube in a small white box, which looked like it might contain a watch. I had a phlebotomist at Megan´s medical practice draw my blood, and I sent the tube off in the mail. The lab would use the blood to determine how my body processes hundreds of drugs. I hoped, in the meantime, that I wouldn´t need Prozac or Oxycontin.