National Health and Nutrition Examination Surveys (NHANES) and Chronic Kidney Disease
Have you been tested for chronic kidney disease?
An important message from diaTribe...
Before you read any further, diaTribe would like to request that you make a note in your diary, Blackberry, Palm Pilot, abacus - whatever works for you - to talk to your doctor about being screened for kidney disease. Some things that indicate you might be at risk for kidney disease include having high blood pressure, obesity or a family history of kidney disease – or just having plain old diabetes, believe it or not. It is recommended that you get blood and urine testing annually if you have diabetes and so if your physician hasn’t recommended you do this – please recommend it to him or her! .
What test do you take? The urine test is called an albumin-creatinine ratio or protein to creatinine ratio. What a mouthful! The blood test is to calculate an estimated glomerular filtration rate (eGFR). An eGFR measures the ability of the kidney to filter toxins from the body. Albumin is a blood protein that when present in urine might indicate kidney damage and is related to an increased risk of heart disease. Early kidney disease often shows few, if any, symptoms until it has progressed to a fairly advanced stage requiring much more involved treatment, so it is important for people with diabetes, obesity, or hypertension to catch it as early as possible by getting tested every year.
Dr. Mary Dittrich of the Boise Kidney and Hypertension Institute, our expert in all things renal (pertaining to the kidneys), explained to us that the blood creatinine value alone is often insufficient to catch early kidney disease. The eGFR adjusts the creatinine levels for age, gender, and race, among other factors, to give a more accurate, meaningful and actionable diagnosis. This is done routinely in some labs or can be done by using an eGFR calculator such as the one on the National Kidney Foundation website. Most labs consider an eGFR value less than 60 ml/min/1.73m2 as abnormal. Dr. Dittrich suggests asking your physician for an eGFR during your next kidney screening and pointed us to the KDOQI guidelines established by the National Kidney Foundation, as well as guidelines from the American Diabetes Association which suggest the following:
Patients with diabetes should be screened annually for diabetic kidney disease. Initial screening should commence:
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Five years after diagnosis of type 1 diabetes or
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From diagnosis of type 2 diabetes
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Microalbuminuria
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Defined as having an albumin-creatinine ratio between 30-300 mg/g
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Macroalbuminuria
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Defined as having an albumin-creatinine ratio over 300 mg/g
… and now, on with the article
In the November 7 issue of the Journal of the American Medical Association (JAMA), Dr. Joseph Coresh and colleagues present data from the National Health and Nutrition Examination Surveys (NHANES), showing that the prevalence of chronic kidney disease (CKD) increased from 10 percent to 13 percent in the US between 1988-1994 and 1999-2004. This extremely dangerous, oft-ignored disease is characterized by permanent loss of the kidney's ability to efficiently remove toxic waste and excess water from the blood. This article calls attention to the under-utilization of CKD screening in the US; according to Quest Diagnostics - which specializes in disease diagnostics – about 60 percent of patients with diabetes and CKD, and 52 percent of patients with diabetes, hypertension, and CKD, did not receive a urine test to check for albumin from 2005-2006, even though yearly screening for CKD is recommended for high-risk patients.
Despite the high incidence of CKD, awareness of the disease in the US remains very low, and a majority of people with CKD are unaware of their condition. This is quite troubling for diabetes given that diabetic kidney disease (nephropathy) results in damage to small blood vessels in the kidneys. Of note, one such substance that stays in the blood due to poor kidney function is insulin, and thus it should not come as a surprise that hypoglycemia is a possible complication of diabetic nephropathy, a cause of CKD.
In this JAMA study, Dr. Joseph Coresh and colleagues estimate the prevalence of CKD in the U.S. using data from the National Health and Nutrition Examination Surveys (NHANES), a national representative sample of over 13,000 U.S. adults. By comparing the prevalence of CKD from NHANES 1999-2004 and NHANES 1988-1994, the authors examine trends in CKD stages and severity. They found that the number of patients with all stages of CKD increased significantly from NHANES 1988-1994 to 1999-2004. Overall prevalence of CKD increased from 10 percent to ~13 percent (or about 20 million adults in the U.S.). This included an increase in stage 1 CKD from 1.7 percent to 1.8 percent; stage 2 from 2.7 percent to 3.2 percent; stage 3 from 5.4 percent to 7.7 percent; and stage 4 from 0.21 percent to 0.35 percent. To put this in perspective, stage 5 CKD is the stage at which renal replacement therapy (RRT) is required in the form of either a kidney transplant or dialysis, in which blood is filtered mechanically outside the body.
diaTribe spoke with Dr. Herman Hurwitz, senior medical director of Quest Diagnostics Incorporated, who underscored that increased awareness and use of a readily available, inexpensive test will be key in reducing the prevalence of CKD.
"Physicians may believe that their patients are not at risk for chronic kidney disease if their blood glucose, lipids and/or blood pressure are controlled. This is simply not true," he said, adding, "Chronic kidney disease is an insidious consequence of these diseases and can progress quickly without routine monitoring. Yet our data suggest that at-risk chronic kidney disease patients are not being monitored as recommended by established guidelines. In this case, the medical community has a tool that, if used well, has the potential to truly make a difference and save lives."
CKD risk factors
The increased CKD prevalence is largely explained by increased prevalence of CKD risk factors - obesity, diabetes, and hypertension - and to a much smaller extent the ageing of the U.S. population. In spite of already high and increasing CKD prevalence, awareness of kidney disease in the U.S. remains very low. Only approximately 12 percent of men and 6 percent of women with stage 3 CKD reported being aware of having weak or failing kidneys. Even with stage 4 CKD, over half of subjects were unaware of their condition. According to a report by Quest Diagnostics, 60 percent of patients with diabetes and CKD, and 52 percent of patients with diabetes, hypertension, and CKD, did not receive a urine test to check for albumin from 2005-2006.
In light of what we have learned about how relatively simple, inexpensive and safe it is to have the test done, these statistics are alarming and we urge you to learn more and help get the word out by checking out the National Kidney Foundation's KEEP Screening initiative. The Kidney Early Evaluation Program (KEEP) offers a free health screening for individuals at increased risk of developing kidney disease. The program recommends that individuals 18 years and older with high blood pressure or with family members who have diabetes, kidney disease and high blood pressure get screened.
These findings demonstrate a failure by medical providers to implement regular CKD screenings as set forth by the guidelines. We learned from our conversation with Dr. Dittrich that nephrology (the specialty of internal medicine that deals with the kidneys) was facing a similar shortage as diabetology/endocrinology, which explains in part the missed opportunities for early CKD detection.
To complete the deadly cycle, this dwindling number of nephrologists find themselves so focused on dealing with end-stage renal disease that they have less time to deal with the milder, nascent cases – which of course results in less opportunity to find and treat early kidney disease and prevent progression to end-stage renal disease. As seems to be the case with diabetes care, the responsibility for early intervention in kidney disease appears to be heading toward the laps of our primary care providers – particularly for asymptomatic conditions such as CKD.
We ask that you do your part as the focal point of your healthcare team and raise the issue of chronic kidney disease at your next physician appointment.
