The perfect dose
Progress: Medicine is hovering on the edge of a real advance: the routine use of genetic testing to predict individual differences in response to medications. To be sure, this kind of testing raises serious ethical questions. A widely supported bill to prevent insurance companies from misusing the information sweepingly passed the House of Representatives and is awaiting introduction in the Senate. But the benefit of the testing is that we may soon be able to modify dosage amounts to reflect our individual differences.
Test: The first great test case for this method is likely to be warfarin. Two million people in the United States use this blood thinner—a medication that blocks the body's production of materials needed for blood clotting—to prevent blood clots, heart attacks, and stroke. It is a drug of great importance, but hard to use because individual differences in patients that derive from small differences in genetic makeup make it hard to get the dose just right. And if it is wrong, a patient is at risk for problems associated with blood clots (like stroke), or for uncontrollable bleeding. Warfarin is the second-most common cause of medication-induced problems that bring patients to the emergency room. (Insulin is the most common cause.)
How it works: Currently, the right dose of warfarin is determined by trial and error: Some medicine is given, the blood clotting is measured, the dose is adjusted, and the patient is again tested and the adjustments fine-tuned. However, until the dose is made perfect the patient may be in danger from overactive or inadequate blood clotting. The differences in response to warfarin are controlled by variants in two genes. Through genetic testing, then, we can largely identify in advance patients who need unusually large or small doses of warfarin for optimum effect.
Cost: It has been persuasively argued that this kind of testing—called "pharmacogenomics"—is highly cost-effective when used to find a good starting dose for warfarin (and soon, I suspect, for other drugs, too). It is estimated that a quick genetic test to establish a best starting dose for warfarin would prevent 85,000 serious bleeding events and 17,000 strokes in the United States alone every year. After accounting for the cost of the testing, the health-care savings are likely to amount to more than $1 billion a year. And a great deal of misery will be prevented.
Conclusion: Such genetic testing is not yet required, but the FDA has just changed the labeling for warfarin products to point out the usefulness of appropriate genetic tests as a first step in determining a patient's optimum dose. I suspect that soon the dose of many drugs will be adjusted in advance to take account of our individual genetic differences. And we will all be much healthier for it.
Maternal weight and birth defects
Question: Overweight people, including pregnant women, are at increased risks for a variety of medical conditions. But what about the babies of pregnant women who are heavy—are they also at higher risk for problems?
New study: It has been suspected that they might be. For instance, there is a clear relationship between certain heart defects in babies and uncontrolled diabetes during pregnancy, a maternal condition often associated with obesity. Now a new and rigorous study gives us better insight into the relationship between maternal weight and infant health. The data come from the National Birth Defects Prevention Study, a study of babies with birth defects born in eight states between 1997 and 2002. D.K. Waller of the University of Texas School of Public Health and colleagues selected more than 10,000 babies with birth defects and examined the pre-pregnancy weight of their mothers. Waller and her * co-authors compared these babies with 4,000 without birth defects to be sure that other qualities that might affect the rate of birth defects—maternal age, smoking habits, education, for instance—weren't significantly different between the groups of mothers. They weren't.