The tens of millions of Americans who take statin drugs to control their cholesterol levels are also taking a calculated risk -- the small chance that they might experience muscle weakness, the most common side effect of the drugs.
Now, British researchers say a screening test that could predict which patients will suffer these side effects may one day be a reality, thanks to their discovery of a gene linked to their occurrence.
But, whether the cost of this potential advance in personalized medicine can justify the returns is still a matter of contention among doctors.
"My first impression is that this is the first time that genomics can be useful in day-to-day clinical medicine," said Dr. Christopher Cannon, a heart researcher at Brigham and Women's Hospital, and an associate professor of medicine at Harvard Medical School, who was not involved with the study. "It seems to be a useful test, and could be one that patients would want to know when they are starting therapy."
Dr. Eric Topol, the chief academic officer of Scripps Health, calls the study a "fantastic jump forward" and says that it is the first to provide strong evidence of a gene that can show potential side effects that will result from a drug.
"It's an exceptionally important one, it's a real major discovery," said Topol. "[It's] not a first, but it's the most impressive one to date."
But, citing cost, not all researchers are so sure about the study's usefulness.
"It is difficult to advocate for an expensive test to determine susceptibility to an adverse effect that occurs in only 1 in 1,000 to 1 in 10,000 patients who take the drug," said Dr. Steve Nissen, chairman of the department of cardiovascular medicine at the Cleveland Clinic, and former president of the American College of Cardiology. "It's nice science, but not a practical screening tool."
Nissen added that since most patients who develop the muscle weakness, known as myopathy, recover completely, any screening test that may be developed in the future may be largely unnecessary.
"The test is designed to determine susceptibility to a non-lethal adverse effect," Nissen said. "If used for all patients starting statin therapy, the costs would be prohibitive."
An estimated 12 to 25 million Americans take some dosage of statins. Researchers found that, among patients who took a more aggressive dose of the drug, roughly 1 in 1,000 were likely to suffer from myopathy, and a common reason why patients stop taking statins -- and most of those cases could be explained by the gene variant.
To find the gene, researchers used a study of 12,000 patients taking an 80-milligram daily dose of statins (the standard dose is 40 milligrams), and looked at the genetic profiles of 85 patients of European descent who were suffering from myopathy. They compared this to the genetic profiles of 90 additional patients, who were similar to the 85, but did not report the side effect.
What the researchers found was that one particular gene variation accounted for 60 percent of the myopathy cases. Similar links between this gene and muscle weakness were seen in patients taking a standard dose of the drug.
The findings are published in this week's issue of the New England Journal of Medicine.