Ask the Doctor
Questions about kidney disease? Risk factors? Signs and symptoms? Are you concerned about yourself, a friend or family member? Ask Dr. Spry.
New York, NY
December 13, 2006
Most Americans now know that they need to watch their blood pressure and cholesterol if they want to avoid heart disease, but very few have the same awareness when it comes to kidney disease. As the second World Kidney Day approaches on March 8, 2007, the National Kidney Foundation (NKF) believes it’s time for Americans to become just as knowledgeable about preventing chronic kidney disease (CKD), the importance of early detection, the one test doctors must perform to diagnose it accurately and what different results, or scores, mean.
Some 20 million Americans – or 1 in 9 adults- suffer from CKD, and another 20 million are susceptible due to risk factors such as diabetes, high blood pressure, cardiovascular disease, family history of kidney disease and racial or ethnic heritage. African-Americans and Native-Americans have a significantly higher risk of developing CKD; rates are also elevated among Hispanics, Asians and Pacific Islanders.
“Most people with chronic kidney disease feel well,” says Allan Collins, MD, president of the National Kidney Foundation. “They have no symptoms. That’s why it’s important for people at risk to have their kidney function tested.”
Physicians perform a variety of tests to assess kidney function. A standard one measures the amount of creatinine, a waste product from muscle activity, in the blood. In healthy kidneys, tiny blood vessels called glomeruli filter creatinine out of the blood. Kidneys with reduced function are less able to perform this filtering job. As a result, blood creatinine levels rise. The standard range for a normal creatinine level is 0.6 to 1.2 mg per deciliter of blood. But this doesn’t take into account critical variables such as age, race, and gender that influence how a test result is interpreted. The only accurate and reliable way to gauge kidney function is to perform an additional calculation that factors in these variables to estimate a patient’s glomerular filtration rate, or GFR.
“Creatinine levels alone are not a sensitive enough test of how well the kidneys are working," says Dr. Collins. “A level of 1.2 could translate into a normal GFR for one person and an abnormal GFR for another depending on these other factors. Also, creatinine levels have an inverse relationship to kidney function. The higher the levels, the lower the kidney function, which can be confusing. GFR estimates are more like a measure of percentage of kidney function, so they’re easier to grasp.” The chart below summarizes what different GFR scores can mean for those at risk for CKD:
Score: 90 or above, other test results normal
Indicates: Normal kidney function
Diagnosis: Increased risk of CKD due to existing risk factors such as diabetes or high blood pressure
Treatment: Regular checkups; usually at least annual testing of kidney function.
Score: 90 or above, other tests results not normal
Indicates: Normal kidney function with protein in the urine or other markers of kidney damage
Diagnosis: Stage 1 CKD
Treatment: Strategies to slow or halt loss of kidney function and minimize risk such as treatment of diabetes, high blood pressure
Score: 60 to 89
Indicates: Mild loss of kidney function with kidney damage such as abnormal urine tests
Diagnosis: Stage 2 CKD
Treatment: strategies to slow loss of kidney function and prevent health complications, such as treatment of high blood pressure and diabetes
Score: 30 to 59
Indicates: Moderate loss of kidney function;
Diagnosis: Stage 3 CKD
Treatment: Consider referral to kidney specialist; strategies to treat health complications such as anemia, bone disease and malnutrition, avoid more serious ones
Score: 15 to 29
Indicates: Severe loss of kidney function; advanced disease
Diagnosis: Stage 4 CKD
Treatment: Recommend referral to a kidney doctor. Strategies to treat complications; preparation for dialysis or transplant
Score: Lower than 15
Indicates: Kidney failure, or end-stage renal disease (ESRD)
Diagnosis: Stage 5 CKD
Treatment: Dialysis or transplant almost always required
The earlier CKD is detected, the better a person’s chances are of working successfully with his or her doctors to slow the loss of kidney function and avoid health problems. That’s another reason early screening is so important. To facilitate early detection, the NKF will offer free medical screenings to people at risk for CKD in at least 20 cities across the country on World Kidney Day, March 8.