Kidney Failure Signaled by Protein

(Ivanhoe Newswire) -- The current system for measuring the severity of chronic kidney disease (CKD) is based on the kidneys' ability to filter and remove waste products -- called glomerular filtration, or eGFR -- with lower eGFR associated with higher risk of adverse outcomes. The system of measurements, however, does not take into account the levels of protein in urine (proteinuria).

In a new study, Canadian researchers were quoted as saying, "… the guidelines have been criticized because they do not incorporate information about the presence and severity of proteinuria an important marker of CKD that is associated with adverse outcomes."

Brenda R. Hemmelgarn, M.D., Ph.D., of the University of Calgary in Alberta, Canada, and colleagues examined the association between reduced eGFR, proteinuria, and adverse clinical outcomes, including all-cause death, heart attack, and progression to kidney failure. The researchers analyzed data from a province-wide Alberta laboratory registry that included eGFR and proteinuria measurements from 2002 to 2007.

The researchers found that within each level of eGFR, there was substantial variability in risk for participants who had greater amounts of proteinuria. Patients with heavy proteinuria but without overtly abnormal eGFR appeared to have worse clinical outcomes than those with moderately reduced eGFR but without proteinuria. Significant interactions between eGFR and proteinuria were observed for death, initiation of renal replacement, and doubling of serum creatinine.

"These findings are important because current guidelines for the classification and staging of CKD are based on eGFR without explicit consideration of the severity of concomitant proteinuria," study authors wrote. "In addition, computerized reporting of eGFR (generally without consideration of proteinuria) is increasingly used to assist physicians in identifying patients at high risk of adverse outcomes -- or those who might benefit from specialist care. Although our findings do not directly address which patients would benefit from referral to a nephrologist, they do suggest that risk stratification performed in terms of eGFR alone is relatively insensitive to clinically relevant gradients in risk. These findings suggest that future revisions of the classification system for CKD should incorporate information from proteinuria."

SOURCE: Journal of the American Medical Association (JAMA), February 3, 2010