Value of screening for kidney disease unclear

NEW YORK Wed Apr 18, 2012 2:41pm EDT

Blood samples wait to be processed at Biobank, the world's largest blood and urine sample freezer near Manchester, northern England, in this March 18, 2010 file picture. REUTERS/Phil Noble

Blood samples wait to be processed at Biobank, the world's largest blood and urine sample freezer near Manchester, northern England, in this March 18, 2010 file picture.

Credit: Reuters/Phil Noble

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NEW YORK (Reuters Health) - Screening people to catch early kidney disease may sound like a good idea, but there is no research to prove that it's worthwhile, according to a new review.

In the U.S., about 11 percent of adults have chronic kidney disease, the vast majority of whom have early-stage disease.

The disease is very common among older adults -- more than 44 percent of Americans older than 70 have it -- and high blood pressure and diabetes are the main risk factors.

In its early stages, chronic kidney disease usually has no symptoms. But there are blood and urine tests that can catch signs of trouble, so it may sound logical to use them to screen everyone for early kidney dysfunction.

The problem is, no clinical trials have tested the effectiveness of widespread screening, according to the new review published in the Annals of Internal Medicine.

Nor have there been clinical trials to see whether routine monitoring of people with early kidney disease improves their long-term outlook.

Controlled clinical trials -- in which people are randomly assigned to have a particular intervention or not -- are considered the "gold standard" of medical research.

"This doesn't mean (screening and monitoring) are not beneficial," said Dr. Howard Fink, a staff physician at the Veterans Affairs Medical Center in Minneapolis, who led the study. "The bottom line is that it's uncertain."

Fink and his colleagues conducted the review of existing research on this subject for the U.S. Preventive Services Task Force (USPSTF), a government-backed advisory group. The panel is currently revisiting its recommendations on kidney cancer screening; right now, there is no recommendation for or against it.

And that's "unlikely to change," given the lack of clinical trials, according to Drs. Katrin Uhlig and Andrew Levey of Tufts Medical Center in Boston, who wrote an editorial published with the review.

Before experts recommend widespread screening for a disease -- which, by definition, means testing symptom-free people -- they want evidence that the benefits outweigh the risks.

"On its surface, it seems like screening for a disease would be beneficial," Fink said in an interview.

But, he said, with any screening test, some people will get "false positive" results. And that will often lead to unnecessary (and possibly invasive) follow-up tests, extra costs and anxiety.

With chronic kidney disease, there have been no studies on the benefits or harms of widespread screening. "Right now, all the screening-related harms are theoretical," Fink said. And so, too, are the benefits.

It's also unclear whether it would be wise to routinely test all people with early-stage kidney disease to see if the problem is worsening over time.

Fink noted that only a small percentage of people with early disease will actually progress to end-stage kidney failure -- at which point dialysis or a kidney transplant are needed.

The review did, however, find evidence that certain kidney disease treatments can slow the progression of the disease.

Fink's team found 110 clinical trial reports on treatments. Overall, two types of blood pressure drugs -- ACE inhibitors and angiotensin II-receptor blockers (ARBs) -- lowered people's risk of developing end-stage kidney disease by about one-quarter to one-third.

But that benefit was largely limited, Fink said, to people with diabetes and high blood pressure, plus large amounts of protein in the urine (known as macroalbuminuria).

Based mainly on one trial, ACE inhibitors seemed to lower death risk in people with diabetes or cardiovascular disease.

According to Fink, if screening is going to work, the "best chance" would come from targeting it to those people who are at increased risk and most likely to benefit from early treatment.

Of course, many people with high blood pressure or diabetes will already be on an ACE inhibitor or ARB, Fink pointed out. So the added value of screening them for kidney disease is still not clear.

On top of that, those same patients will usually automatically have their glomerular filtration rate (GFR), an important measure of how well the kidneys are working, reported after routine blood work at their doctor's office, said Uhlig.

"This diminishes the benefit from screening," she told Reuters Health in an email.

For patients, the main thing is to get their risk factors for kidney disease under better control, according to Uhlig.

"Even without strong evidence on the benefits of screening for chronic kidney disease," she said, "risk factors like hypertension (high blood pressure) and diabetes require treatment to avoid kidney disease, as well as cardiovascular disease."

As for people who already have early-stage kidney disease, some type of monitoring is needed, according to Uhlig.

"However," she said, "how often and how depends on many factors: the type of disease, the speed with which the disease progresses, treatments, other healthcare problems."

SOURCE: bit.ly/HTd5UT and bit.ly/HQmU1p Annals of Internal Medicine, April 17, 2012.

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Comments (1)
guineapig07 wrote:
I found out I had Kidney disease when I was in 11th grade, which for the type I had was pretty rare for my age. I believe that there is a reason for screening because just because most people have it when they are older does not always mean that is the case. I believe mine was in a very early stage but if I had not found out then who knows what could have happened. I was treated for it with a very high and long term doses of steroids. (when you get a steroid shot at the doctor it is about 10mg)(mine was a pill and the most I had to take was 100mg) It was a very hard thing to do/overcome but I am in better health for it now. I have never met anyone who has kidney disease or the type i have for that matter but I am living proof that it does matter about the testing and they should try to save everyone they can. For everyone else who is out there that survived it you are a strong person and you should never thing otherwise.

Apr 18, 2012 1:03pm EDT  --  Report as abuse
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