Healthy people with high urinary protein levels have elevated kidney disease risk

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Ronald T. Gansevoort, MD, PhD

Measuring the amount of protein lost in the urine can identify individuals at risk of developing kidney disease, according to a study appearing in the April 2009 issue of the Journal of the American Society Nephrology (JASN). The results suggest that a simple and low-cost urine screen is a promising way to address the epidemic of chronic kidney disease (CKD). More and more individuals are diagnosed with CKD each year, but many people are unaware of their risks of developing the disease. Researchers have been looking for ways to screen the population to identify people at high risk for kidney function loss at an early stage so that preventive measures can be taken. Now investigators have found that screening urine samples is a promising strategy.

In a study led by Ronald T. Gansevoort, MD, PhD, of the University Medical Center Groningen in the Netherlands, more than 40,000 individuals of the general population were asked to collect a urine sample in a plastic test tube. Samples were sent to a central laboratory where their protein concentrations were measured. The investigators continued to follow these individuals and noted who developed end-stage kidney disease over the next nine years. A subgroup of 8,592 subjects visited an outpatient department once every three years allowing a detailed study of the rate of kidney function decline during follow-up.

Subjects from the general population that were found to have increased urinary protein levels were shown to represent more than half of the patients who started dialysis or had a kidney transplant during follow-up. Restricting screening to those individuals with hypertension, diabetes, cardiovascular disease history, or age >55 years having increased urinary protein levels identified nearly all cases needing kidney disease treatment during follow-up.

The researchers concluded that individuals with high urinary protein levels are at high risk for losing their kidney function and needing dialysis or a kidney transplant. The higher the level of proteins in the urine, the higher the risk of needing dialysis or a kidney transplant and the more rapid the rate of kidney function decline.

"Our findings suggest that subjects with a high amount of urinary protein loss should be invited to a medical center for further investigation and for start of preventive treatment to protect the kidney," said Dr. Gansevoort. While our group already showed this approach to be cost-effective to prevent cardiovascular events, additional studies are needed to determine if performing urine screens in the general population (or in certain high-risk groups of individuals) would even be more cost-effective because need for dialysis may also be prevented.

Source: American Society of Nephrology