To Screen or Not to Screen?

May 31, 2011

In May, a collection of academics, physicians, scientists, and activists were convened by the Novartis Institutes for Biomedical Research to discuss the current state of global health equity, or why certain populations continue to suffer from illness and disease at a rate disproportionate to other populations.

Many of the presentations focused on socioeconomic disparities as a barrier to access: lack of transportation, lack of quality education, the high price of a healthy diet, and clean air. (One slide featured an aerial photograph of Chicago, in which the positive correlation between amount of trees on a given block, and household income, was outlined with startling precision.) These are complex issues requiring complex solutions. If government leaders with both the inspiration and power to enact change are few and far between, and the prevailing ethos among the moneyed classes is one of "personal responsibility"—as opposed to civic duty—then what else can be done?

Pharmacogenomic research and new drug development, that's what. But first, you'll need to be screened, to determine what sort of human being you are, genetically speaking. "How much 'Asian' do you have in you?" asked Charmaine Royal, PhD, associate research professor at the Duke Institute for Genome Sciences & Policy, imitating the awkward conversation a doctor might need to have with a patient, after it was discovered that carbamazepine (Carbatrol, Equetro, Tegretol) can cause "serious and sometimes fatal dermatologic reactions" in patients with the HLA-B*1502 allele, which, it turns out, is found "almost exclusively in patients with ancestry across broad areas of Asia," according to FDA's black box warning.

If a strong correlation can be shown between the presence of a genetic marker and drug toxicity, it follows that new drugs targeting ethnic populations with high incidences of a given disease can be developed to focus on genetic markers and drug efficacy, right? Not exactly. That premise assumes that ethnic groups, or different "races," are to some important degree homogeneous, genetically. The truth is a bit muddier. The IL28B gene, for example, has been shown to predict hepatitis C treatment-induced viral clearance, but it's not exclusive to a particular "race"—it occurs to a varying degree in all "races." The word race is deserving of quotation marks because it's a somewhat arbitrary designation; racial and ethnic categories have changed every 10 years on the US Census.