Researchers recommended making chronic kidney disease (CKD) a coronary heart disease risk equivalent after their results showed the risk of MI was similar for CKD and diabetic patients in a study published online June 19 in The Lancet. Writers in an accompanying editorial praised the study despite its falling short on its primary outcome.

Marcello Tonelli, MD, of the department of medicine at the University of Alberta in Edmonton, Canada, and colleagues posed the question: Given the high rates cardiovascular (CV) events in patients with CKD, should CKD be considered a risk equivalent for heart disease? The authors argued that the U.S. National Cholesterol Education Program Adult Treatment Panel III guidelines for cholesterol lowering therapies already classify diabetes as a risk equivalent based in part on data linking diabetes and the risk of CV events.

The researchers used the Alberta Kidney Disease Network database in Canada to obtain routine laboratory data from all patients in Alberta. They selected patients who were 18 years or older who had serum creatinine measured at least once as an outpatient between 2002 and 2009. They excluded patients with an estimated glomerular filtration rate (eGFR) indicating end-stage kidney disease. Of those remaining, they identified patients who also had been tested for proteinuria.

They defined CKD as eGFR lower than 60mL/minute per 1.73 m² (stage 3 or 4). They followed patients from their index date until March 31, 2009. The primary outcome was first MI admission to a hospital and the secondary outcome was all-cause mortality. Using the Alberta Bureau of Vital Statistics, they also assessed short-term and long-term mortality after MI.

One percent of the patients were admitted to a hospital for MI during a median 48-month follow-up. Those with a previous MI had the highest unadjusted rate of MI (18.5 per 1,000 person years). In those with no previous MI, patients with diabetes and no CKD had a rate of 5.4 per 1,000 person-years while patients with CKD and no diabetes had a rate of 6.9 per 1,000 person-years. Adjusted relative rates of MI, though, were similar for patients with CKD and severely increased proteinuria and those with diabetes.

But the proportion of patients who died within 30 days of admission for MI was much higher among patients with CKD and no diabetes, at 14 percent, than for those with diabetes and no CKD, at 8 percent. It even topped the proportion of patients with a history of prior MI, at 10 percent.

“Our findings show that the risk of myocardial infarction in people with chronic kidney disease and proteinuria is similar or greater than the risk in those with diabetes,” the authors wrote. “The rate of mortality after myocardial infarction in our study was significantly higher in participants with chronic kidney disease than in those with diabetes.”

The authors concluded that their findings support adding CKD to the list of criteria when defining those at high risk of future coronary events. “Our research suggests that there is a strong case for considering chronic kidney disease to be a coronary heart disease risk equivalent, meaning that people with chronic kidney disease are at a comparable risk of coronary events as those who previously had a heart attack,” Tonelli said in a release.

In an accompanying editorial, Tamar S. Polonsky, MD, and George L. Bakris, MD, both University of Chicago Medicine in Chicago, pointed out that the study had negative findings in the primary outcome: first MI admission to a hospital. They also addressed limitations, including the lack of information about individual patient’s medications and efforts to control CV risk factors.

But they praised the study’s use of a population-based cohort of almost 1.3 million people in a real-world setting and its findings. “Tonelli and colleagues offer new insight by comparing individuals with chronic kidney disease with those who have a history of myocardial infarction, on a very large scale,” they wrote. “Their findings emphasize the importance of primary prevention, particularly because patients with chronic kidney disease comprise a large proportion of the patients who have myocardial infarction.”