These drugs are being tested in large clinical trials to see if their effects on LDL levels translate into reduced incidences of heart attacks, strokes and death. The Food and Drug Administration has approved the drugs based on their LDL-lowering effects for a number of patient groups, including those at high risk for heart disease who report painful muscle aches or weakness when they take statins.

The PCSK-9 inhibitors can cost more than $14,000 a year, while statins can cost just pennies a day, so determining what portion of patients are truly statin intolerant has become an important question.

A second study presented at the cardiology meeting on Sunday and published online in JAMA, the Journal of the American Medical Association revealed just how vexing the issue is.

The study, directed by Dr. Nissen and paid for by Amgen, a pharmaceutical company, included more than 500 people with extremely high levels of LDL cholesterol who had tried two or more statins and had reported aching or weak muscles so severe that they said they absolutely could not continue taking the drugs.

The participants were randomly assigned to take either a statin, atorvastatin or a placebo for 10 weeks. Then those taking a statin were switched to a placebo for 10 additional weeks, and those taking a placebo were switched to a statin. The result: Less than half of the patients seemed to be truly unable to tolerate statins, and complained of muscle pain only when they were taking the drug. A quarter of the patients reported muscle problems with a placebo. And nearly one in 10 had muscle issues with both the statin and the placebo.

That indicated that 57 percent of patients actually could tolerate statins. Researchers then randomly assigned the remaining 43 percent to take either Amgen’s PCSK-9 inhibitor, evolocumab, or another cholesterol-lowering drug, ezetimibe, which is often taken by statin intolerant patients but has never been shown to reduce heart disease risk when taken without an accompanying statin. The patients tolerated both drugs.

The statin tolerance results were not a total surprise. Smaller studies had indicated that most patients who said statins caused muscle aches actually could tolerate the drugs. But this was the largest such study and raised a real question about how to treat patients who are at high risk of heart disease and say they cannot or will not take a statin because of intolerable side effects.