Doctors have long recognized that heart attacks and strokes are more common in people with severe chronic kidney disease. Yet studies show that many physicians are not aware of the cardiovascular risks associated with the early stages of kidney disease. Doctors are also failing to check for it appropriately in their patients.

People with diabetes are more prone to develop kidney disease. In these patients, testing for small quantities of albumin in the urine (microalbuminuria) can identify kidney disease in its earliest stages and treating it then can slow its progression.

Microalbuminuria also occurs in people with kidney damage from other causes, such as high blood pressure, but the test is most often carried out in people with diabetes. Chronic kidney disease is also more common in older people even when they do not have diabetes. Yet studies show that doctors often don't recognize its early stages in this group.

To assess kidney function, physicians tend to rely on blood levels of creatinine, which is formed in the body and excreted in the urine. Although blood creatinine levels do rise slowly as kidney function deteriorates, creatinine is not a reliable measure of early kidney damage.  

The best way to determine how the kidneys are working is by measuring the glomerular filtration rate (GFR). A decline in GFR accompanies the early stages of chronic kidney disease. Many laboratories are now reporting the GFR when a doctor orders a blood creatinine test. An estimated GFR of less than 60 ml per minute is the standard criteria for the diagnosis of chronic kidney disease, which in turn is associated with an increased risk of cardiovascular disease.  

An additional new test for kidney function measures blood levels of a protein called cystatin C. Like creatinine, cystatin C is formed in the body and is exclusively removed by the kidneys. Some studies suggest that blood levels of cystatin C may allow a more accurate estimate of GFR than blood levels of creatinine.

If you are older than 50 or had some previous kidney problem, ask your doctor about your GFR. The query might motivate him or her to order a test for GFR if it hasn't already been done.