Simple tests used regularly to assess kidney function and damage also could help doctors predict who will suffer heart disease, the nation's leading cause of death, researchers from the Johns Hopkins Bloomberg School of Public Health have found.
The tests are just as good, if not better than, standard cholesterol and blood pressure tests, potentially giving doctors a better idea of which patients to more closely watch or treat, said Dr. Kunihiro Matsushita, an assistant scientist in the school's department of epidemiology who led the research.
"Cholesterol levels and blood pressure tests are good indicators of cardiovascular risk, but they are not perfect," he said. "This study tells us we could do even better with information that oftentimes we are already collecting."
The tests assess kidney function by measuring a waste product in blood called creatinine and kidney damage by measuring a protein in urine called albumin.
The tests are frequently used because kidney disease is common, with 26 million in the United States suffering, and many professional associations as well as official government advisers recommend them to track people with diabetes and hypertension, as well as kidney disease.
The kidney function test, called estimated glomerular filtration rate or eGFR, is given 290 million times a year, the researchers said.
Matsushita is thinking about developing calculators that could more specifically spell out how much more risk different people of different nationalities and backgrounds face based on increases in creatinine and albumin levels.
That way doctors would have a better handle on how much risk individuals have particularly for heart failure, when blood isn't pumping normally; heart attack, when a clot blocks normal blood flow; or stroke, when a clot blocks blood flow to the brain.
They could prevent some deaths and disabilities by recommending medications or lifestyle changes such as increased exercise or improved diet.
Federal data show that every year in the United States, more than 735,000 people have a heart attack and 610,000 people die of heart disease.
Only about half of those with heart disease have an indicator such as high blood pressure or high cholesterol, or smoke, according the U.S. Centers for Disease Control and Prevention.
Researchers don't fully understand why there is such a strong association particularly between kidney damage and risk of heart trouble. But they said those with chronic kidney disease have twice the chance of developing cardiovascular disease than those with healthy kidneys.
Researchers at Hopkins' Chronic Kidney Disease Prognosis Consortium analyzed data from 24 studies, including more than 637,000 people with no history of cardiovascular disease and the results of their kidney function and damage tests.
They found albumin specifically was a better predictor than standard tests in general, and an even stronger predictor in African-Americans. Generally, the higher the albumin level, the higher the risk.
The tests are still not likely to be used on the general population to predict heart disease, said Dr. Josef Coresh, coordinator of the Hopkins kidney consortium and director of the Bloomberg School's G.W. Comstock Center for Public Health Research & Prevention.
The U.S. Preventive Services Task Force, which advises the government, doesn't recommend the tests for adults with no symptoms of kidney disease.
But some believe that the findings, published in May in the medical journal Lancet Diabetes and Endocrinology, support using the tests on people who are at risk of cardiovascular disease.
That would help doctors intervene "and save lives," said Dr. Leslie Spry, the medical director of the Dialysis Center of Lincoln in Lincoln, Neb., and a spokesman for the National Kidney Foundation.
More kidney patients die of heart maladies than wind up in end-stage kidney disease and on dialysis, but there hasn't been a way to predict which ones would have heart problems.
"In my 30 years of doing this, I've always felt people with kidney disease and protein in their urine were a different breed than people who don't have the protein," Spry said. "If you have the albumin you have a greater chance of dying of heart disease. They've made the link."
He said more people should be advised to diet and exercise, quit smoking and even go on medications, he said. There also should be more trials to see if statins widely used to lower cholesterol in heart patients are safe for kidney patients.
Dr. Jeffrey Quartner, chief of cardiology at MedStar Union Memorial Hospital, agreed that it would be helpful to know earlier who might develop potentially fatal heart problems.
He said the kidney tests could serve as a "red flag" and could add to the overall evaluation of a patient. But he cautioned that it should not be the only test a doctor considers.
A full evaluation, considering all the risk factors — such as other health problems, lifestyle choices and family history — would help a doctor determine if steps such as medications are necessary, he said.
Quartner called the study a "good first observation" and said calculators showing more specific risk would be even more helpful.