Tests are conducted to assess how well the kidneys filter out creatinine from the body around 290 million times a year.
"If health care providers have data on kidney damage and kidney function - which they often do - they should be using those data to better understand a patient's risk of cardiovascular disease," says Dr. Kunihiro Matsushita, an assistant scientist in the Bloomberg School's Department of Epidemiology and lead author of the study.
Patients with chronic kidney disease are twice as likely to develop cardiovascular disease than those whose kidneys are healthy. According to the authors of the study, roughly half of patients with chronic kidney disease die of cardiovascular disease before developing end-stage renal disease.
Dr. Matsushita explains that while traditionally-used cholesterol levels and blood pressure tests are good indicators of cardiovascular risk, they are not perfect. "This study tells us we could do even better with information that often times we are already collecting."
Two key tests that help define and stage chronic kidney disease identified by the researchers are those that check the blood for creatinine and those that measure the amount of albumin in the urine.
Creatinine is a waste product of the muscles and the amount of it that is in the blood indicates how well the kidneys are filtering it out of the body. Testing how well the kidneys are filtering it out - referred to as an estimated glomerular filtration rate (eGFR) - is carried out an estimated 290 million times annually in the US.
Albumin is a protein that leaks out of the kidney into the urine. If there are high amounts of this protein present then it is likely that the patient has kidney damage. Measuring albuminuria is also common in the US, particularly among patients with diabetes and hypertension.
According to the authors of the study, the data provided by these tests could help physicians when making decisions about forms of treatment such as statins, or whether patients need lifestyle interventions such as improved diets and exercise.
Findings 'lend support to including kidney tests in cardiovascular risk assessments'
For their meta-analysis, researchers examined data obtained from 24 studies included in the Chronic Kidney Disease Prognosis Consortium. These studies involved a total of 637,315 participants without a history of cardiovascular disease and with results for eGFR and albuminuria tests.
In these cohorts, the researchers found that eGFR levels and albuminuria both independently improved prediction of cardiovascular disease. In particular, these tests improved prediction of heart failure and death from heart attack and stroke.
Between the two, albuminuria was found to be the stronger predictor, even outperforming cholesterol levels and systolic blood pressure as a risk factor for these cardiovascular problems. The researchers found that albuminuria is a stronger predictor than these two traditional test measures even when the subject is a smoker.
At present, many clinical guidelines recommend patients with diabetes, hypertension and potential chronic kidney damage should be assessed for kidney function and kidney damage. Dr. Matsushita suggests the findings of the study show that others not covered by these guidelines may also benefit from these kidney tests.
Although it is not fully understood precisely how kidney disease is linked with cardiovascular disease, Dr. Matsushita says that a fluid overload caused by kidneys not functioning correctly can lead to heart failure.
"In populations with chronic kidney disease, the simultaneous assessment of eGFR and [albuminuria] could facilitate improved classification of cardiovascular risk, supporting current guidelines for chronic kidney disease. Our results lend some support to also incorporating eGFR and [albuminuria] into assessments of cardiovascular risk in the general population," conclude the authors.
Previously, Medical News Today reported on a study that overturned what was previously believed about the use of injured kidneys from deceased donors for transplant. Researchers suggest that such kidneys may be more viable for transplant than is commonly assumed.