SAN DIEGO — Elevated baseline cystatin C levels in patients who present with acute coronary syndrome are strongly linked with adverse cardiovascular outcomes, results from a large study showed.
“Cystatin C has been shown to be a strong and independent predictor of cardiovascular events and overall mortality in elderly subjects, but its prognostic performance in patients with acute coronary syndrome is less well studied,” reported Dr. Stacy E. Melanson on behalf of coauthor Dr. Steven D. Wiviott and researchers from the Thrombolysis In Myocardial Infarction (TIMI) Group at Brigham and Women's Hospital, Boston.
In a poster presented at the annual meeting of the American Association for Clinical Chemistry, the researchers analyzed levels of cystatin C in blood samples from 3,754 patients that were collected within 10 days of presentation with ACS. The primary end points were death, MI, and heart failure. The researchers determined cardiovascular outcomes for each quintile of cystatin C. Cut points for cystatin C, in mg/L, were: less than 0.82 for quintile 1; 0.83–0.91 for quintile 2; 0.92–1.00 for quintile 3; 1.01–1.14 for quintile 4; and 1.15 or more for quintile 5.
Patients who had elevated cystatin C levels were more likely to have hypertension, diabetes, and a history of MI. They were also more likely to be older. Specifically, the median age of patients in quintile 5 was 68 years, while the median ages of patients in quintiles 1, 2, 3, and 4, were 52, 54, 57, and 61 years.
Between cystatin C quintiles 1 and 5, the risk of death rose from 0.7% to 4.8%; the risk of MI rose from 5.4% to 10.6%; the risk of heart failure rose from 1.0% to 8.3%; and the risk of a composite of death and heart failure rose from 1.7% to 11.6%.
After the researchers adjusted for clinical variables, they found that cystatin C levels in quintile 5 independently predicted recurrent events, compared with the levels in quintile 1. Specifically, the hazard ratios between quintile 5 and quintile 1 were 2.5 for death, 1.6 for MI, 4.2 for heart failure, and 3.1 for a composite of death and heart failure.
When other markers of hemodynamic stress were added to the model, including C-reactive protein and B-type natriuretic peptide, cystatin C remained a significant predictor of recurrent cardiovascular events.
Dr. Melanson is associate medical director of clinical chemistry at Brigham and Women's Hospital.