Protein in urine as sign of kidney disease important indicator of risk of death and cardiovascular disease

For people with chronic kidney disease protein loss in the urine appears to be just as important an indicator for the chances of death and the risk of cardiovascular disease as the degree of renal function loss. This has been revealed by a meta-analysis conducted by kidney researchers from the University Medical Center Groningen/University of Groningen and the University of Baltimore.

On behalf of an international consortium of kidney specialists, they analysed 21 population studies in which over one million people from 14 countries participated. The results of this study indicate that the international guidelines for the detection and treatment of people with chronic kidney disease should be revised. The researchers, headed by nephrologists Paul de Jong and Ron Gansevoort of the UMCG, will be publishing the results today in the renowned scientific journal The Lancet.

Chronic kidney disease occurs in about ten percent of the adult population. Thus far, the prognosis for people with chronic kidney disease is based on the amount of renal function loss – the less the ability of the kidneys to process waste products, the lower the life expectancy. This study, however, shows that in addition to renal function, the degree of protein loss in the urine is also an important prognostic parameter. Besides the level of renal function, more protein in the urine is an indication of a lower life expectancy and a greater chance of cardiovascular disease.

Various studies with data on protein loss and renal function were involved in this meta-analysis. The researchers analysed the results of 21 population studies. A total of no fewer than one million patients from 14 countries were involved. The studies investigated protein loss using two methods. The findings were identical, regardless of whether the urinary protein loss was measured with a precise, expensive system or with a very cheap screening test. The cheaper test was used in many of the larger population studies; the Dutch guidelines recommend using the more expensive method.

This meta-analysis has revealed that the predictive value of protein loss and renal function is independent of the presence of other known risk factors for cardiovascular disease, such as smoking, obesity, diabetes, high blood pressure and a high cholesterol.

The chances of dying are increased by 57 percent for a person with slightly impaired renal function, which is present in out at about 1.5 percent of the population. The chances of dying are increased by 63 percent for a person with a limited amount of protein in the urine (microalbuminuria), which is present in about 7% of the population.

The results of this study indicate that the international guidelines for the detection and treatment of people with chronic kidney damage should be revised. The accompanying editorial in The Lancet says that these findings indicate that if doctors want to make an accurate prediction for a patient of the chances of cardiovascular disease, they must not only take the usual risk factors into account, but also the signs of chronic kidney disease.

This study was financially supported by the KDIGO, US National Kidney Foundation and the Dutch Kidney Foundation.