Cystatin C Superior for Predicting Death Risk

Cystatin C values are significantly associated with all-cause mortality, whereas creatinine-based estimates are not.
Cystatin C values are significantly associated with all-cause mortality, whereas creatinine-based estimates are not.

Cystatin C is a better predictor of all-cause mortality risk than creatinine-based estimates of glomerular filtration rate, according to a new study.

The study, led by Marika Salminen, MD, University of Turku and Turku University Hospital, Turku, Finland, included 1260 individuals with a mean age of 74 years. During a 9-year follow-up, 275 died, 192 from cardiovascular disease (CVD). The investigators compared cystatin C with the Modification of Diet in Renal Disease study equation and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and the combined creatinine-serum cystatin C (CKD-EPIcr-cys) equations.

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After multivariable adjustment, only cystatin C values predicted all-cause mortality in fully adjusted models. Each 0.1-unit increment in cystatin C concentration was associated with an approximately 10% increased the risk of death from all causes, Dr. Salminen's group reported online ahead of print in the European Journal of Internal Medicine. Results also showed that each 0.1-unit increment in cystatin C concentration was associated with a significant 10% increased risk of both cardiovascular and non-cardiovascular death in men and a significant 9% and 13% increased risk of cardiovascular and non-cardiovascular death in women, respectively. The CKD-EPIcr-cys equation remained a significant predictor of non-CVD deaths among women, with each 0.1-unit increase in CKD-EPIcr-cys value associated with an 8% increased risk of non-CVD death.

“Our results suggest that cystatin C is an accurate measure of the risk of death in elderly men and women, and using the combined CKD-EPIcr-cys equation does not provide any additive prognostic information,” the investigators wrote.

Dr. Salminen and colleagues noted that it has been argued that cystatin C may have toxic effects that contribute to its association with death. “We cannot exclude the possibility that the prognostic ability of cystatin C may be mediated in part by some other factor than impaired kidney function,” they stated. “Nevertheless, contrary to cystatin C, all creatinine-based eGFR equations lost their predictive value for death in the fully adjusted model. Thus, although there may be non-GFR factors that affect the serum concentration of cystatin C, it seems to be a strong estimate for the risk of death in elderly subjects.”

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