Here's a quick quiz: what's the world's No. 1 killer? It's not AIDS, TB or malaria. The world's deadliest disease is heart disease, which kills nearly 18 million people a year. Once considered predominantly an affliction of the wealthy, the prevalence of heart disease has been growing in the developing world 80% of heart-disease deaths now occur in low- and middle-income countries, which has got global health workers and epidemiologists considering better ways to screen, track and treat the illness.
Now it looks like screening, at least, could get a whole lot cheaper and faster. A team of U.S. researchers publishing this week in the medical journal Lancet finds that simple, inexpensive tests for cardiovascular risk factors performed in less than 10 minutes, using a scale, a tape measure and a blood-pressure check are every bit as effective at determining heart-disease risk as more expensive procedures involving laboratory-based tests. It's not exactly a do-it-yourself kit, but it can help doctors screen patients more quickly, leading to potentially more effective treatment in both the developed and developing world.
The researchers, led by Thomas Gaziano at Harvard Medical School and Brigham & Women's Hospital in Boston, trawled through data on 6,186 American adults participating in the U.S. National Health and Nutrition Examination Survey. Participants were initially examined in the early 1970s and had no prior history of cardiovascular disease; they were tracked for 21 years, during which time 1,529 of the participants suffered cardiovascular events (such as heart attacks, stroke, angina or heart failure), including 578 deaths due to heart disease.
Researchers looked at patient measurements typically used to assess heart disease risk: age, systolic blood pressure, smoking status, total cholesterol, diabetes status and any hypertension treatment. They found that they could substitute body mass index (or BMI, a ratio of height to weight), a noninvasive measure, for the lab-based blood test for cholesterol and still accurately predict patients' five-year cardiovascular disease risk.
Gaziano and his colleagues show that if simple measurements, like BMI, are thoughtfully considered, doctors with fewer resources in the developing world can screen for heart-disease risk just as effectively as their counterparts in high-income countries. There is some question about whether results from the U.S. can be applied accurately to other populations for a given BMI, for example, Asians tend to have a higher body-fat ratio than Caucasians but, in many ways, Americans of the 1970s may be more similar than not to populations elsewhere today. In the '70s, Americans smoked a lot more tobacco than today, and few were getting treatment for high blood pressure or high cholesterol. That's not so different from 21st-century Russians or Eastern Europeans, Gaziano suggests.
A second article in this week's Lancet shows that heart-disease risk factors are rapidly becoming more common worldwide, even in sub-Saharan Africa, where infectious disease remains a big killer. In theory, African doctors should be among those who benefit most from the new paper's findings. In resource-poor settings, saving the $1 to $3 cost of a lab blood test (in the U.S. it costs $10, according to the Lancet paper) would certainly be meaningful but that's assuming the tests were being performed to start with. The real savings are difficult to calculate, in large part because the populations most likely to benefit from dropping lab tests are those that are least likely to have any labs or technicians available be doing them at all.
The reality is that some developing countries spend as little as $30 a year per person in health care costs; the rich world spends thousands. For patients in low- and middle-income countries, meaningful costs also include the cost of taking time off work to take the test, then traveling back to the clinic for the results. For those reasons, the World Health Organization's current guidelines for assessing cardiovascular disease risk where lab resources are scarce have already dropped the cholesterol testing.
The new findings may in the end offer more cost-saving potential and raise more interesting questions in developed nations, including the U.S., where medical costs have spiraled upward in the last two decades. Neither doctors nor patients may want to drop cholesterol testing altogether more information is better, especially when the consequence of missing a diagnosis is heart attack but there is still a practical lesson to be learned. "I think in the U.S. we might use this as an initial test," Gaziano says. "We can at least narrow the group of people for whom we need to screen cholesterol." Those with very few other heart-disease risk factors, for example, probably don't need the extra blood work, since their cholesterol profile wouldn't make a big difference to overall risk anyway. Similarly, those patients with several risk factors for heart disease probably need treatment no matter what their cholesterol levels. By giving blood tests only to those on the fence, doctors can save resources for the tests and treatments that are warranted.