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

Bone mineral density loss faster in those with kidney disease

By American Journal of Kidney Diseases, [RxPG] Even slight kidney impairment can speed up the loss of bone mineral density (BMD) among older people, putting them at risk of potentially disabling fractures, new research shows.

“Our findings highlight the importance of estimating kidney function when evaluating patients for fracture risk,” Sophie A. Jamal, MD, PhD, of the University of Toronto and her colleagues say in the February issue of the American Journal of Kidney Diseases, the official journal of the National Kidney Foundation.

Most people who have chronic kidney disease (CKD), or who are at risk for this condition, don’t know it, points out Dr. Kerry Willis, senior vice president for scientific activities at the National Kidney Foundation. “The new findings show the potential impact of early identification of kidney disease in preventing complications that can cause disability and premature death,” Dr. Willis said.

When a person’s kidney function is completely lost—a condition known as end-stage renal disease—he or she is at much greater risk of sustaining a hip fracture, Dr. Jamal and her colleagues explain in their report.

To better understand the relationship between more modest kidney impairment and bone loss, the researchers followed 191 men and 444 women age 50 and older for five years. They used two different techniques—estimated creatinine clearance and estimated glomerular filtration rate—to gauge patients’ kidney function at the beginning of the study. The first test measures how quickly the kidneys clear creatinine (a waste product), from the blood, and the second gauges the speed at which fluid flows through the kidney. Study participants also had their BMD measured at the beginning of the study and five years later.
Dr. Jamal and her team found that the people with impaired kidney function lost BMD faster than those whose kidneys were working normally. For example, the study participants with the worst kidney function showed a 9.3 percent greater decrease in their lower spine BMD over a five-year period compared to those with normally functioning kidneys. The results were basically the same with either kidney function measure.

“Not only is this a substantial loss, but equally concerning is that the bone loss occurs with even modest impairment of kidney function,” Dr. Jamal and her colleagues say.

To date, the National Kidney Foundation’s Kidney Early Evaluation Program (KEEP) has screened 130,000 high-risk individuals for CKD, Dr. Willis said. Anyone 18 and older who has high blood pressure, diabetes or a family history of kidney disease should be screened for CKD, she added, which can be done with three simple tests: blood pressure measurement, a urine test for the presence of a protein called albumin, and a blood test for creatinine.

“Osteoporosis can lead to potentially disabling fractures of the spine and hip,” she added. “Physicians should understand that even a slight decline of kidney function in their older patients could mean an increased risk of osteoporosis.”



Publication: February issue of the American Journal of Kidney Diseases