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Kidney disease overdiagnosed, study suggests

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If the public has learned anything about medicine during the COVID-19 pandemic, it is that science is constantly evolving. New findings can change how experts define a given illness, as well as how they diagnose, prevent and treat it.

Such is the case, a new study suggests, with chronic kidney disease. A growing cadre of physicians are combating what they call an overdiagnosis of this condition in the elderly. According to these doctors, many older adults who’ve been told their kidneys are on the road to failure may not have anything more than a normal age-related decline in kidney function. For many, their kidney disease is unlikely to become a medical problem during their remaining years of life.

This, in fact, is exactly what happened to a friend’s mother who was told she had kidney disease in her late 70s. She received drug treatment for the disorder and recently died at 92 of a combination of old age, malnutrition and bedsores, but with kidneys that still worked perfectly.

Yet being told that organs as important as one’s kidneys are functioning poorly may cause older people needless emotional distress. In addition, doctors may too readily prescribe medications, including drugs that lower blood pressure, that have financial costs and side effects.

Life-sustaining filtration

Most people are born with two kidneys, which work as the body’s filtration system. Each bean-shaped organ has about a million units called nephrons. And each nephron contains a glomerulus, a tuft of tiny vessels that filters the blood as it passes through, and a tubule that sends cleansed blood and essential nutrients back into circulation. In the course of a day, some 150 quarts of blood normally pass through the kidneys, with only a quart or two of liquid waste leaving the body as urine.

Health care workers typically assess how well someone’s kidneys work by starting with a blood test for the glomerular filtration rate, or G.F.R., an estimate of how much blood passes through the glomeruli every minute. If the estimated G.F.R. is abnormally low, the patient’s urine is analyzed for the level of protein, or albumin, being excreted. If that is high, it could indicate poorly functioning kidneys.

According to current guidelines, an estimated G.F.R. below 60 for three months or longer is considered an indication of chronic kidney disease. While a rate below 60 would indeed be worrisome for a 50-year-old, for people in their 70s and 80s it may simply reflect the normal slowing of a bodily function with age, the new research suggests.

What the study found

The new research, published in JAMA Internal Medicine in August, found that many people over 65 with a low estimated G.F.R. and no elevated protein in their urine did not have increased health risks.

For the study, Dr. Pietro Ravani, a nephrologist at the Cumming School of Medicine at the University of Calgary in Alberta, and his co-authors analyzed health data collected from 127,132 men and women in Canada. They compared the risk of kidney disease and death over five years based on their G.F.R.

The fate of those with a G.F.R. of less than 60 — which would result in a diagnosis of chronic kidney disease using current guidelines — was then assessed according to two different criteria. One was based on the fixed rate of 60, and the other with a sliding G.F.R. that was adjusted for age, ranging from younger than 40 to older than 65.

The researchers found that in younger adults, a G.F.R. of 45 to 59 would indicate declining kidney function that warrants careful monitoring and treatment. But in older adults, particularly those in their 80s and beyond, the risk of kidney failure associated with such a low G.F.R. was essentially the same as those with a G.F.R. of 60 or above. In fact, the risk of death from kidney failure up to and beyond age 100 was no different at any age over 65.

In 2008, two nephrologists debunked the supposed “epidemic” of chronic kidney disease that stemmed from diagnostic guidelines issued in 2002. Although revised guidelines in 2012 further narrowed the definition of who has chronic kidney disease, the new study suggests guidelines need yet another refinement.

Competing interests

In an editorial accompanying the new report, Dr. Ann M. O’Hare, a nephrologist at the University of Washington and the VA Puget Sound Health Care System in Seattle, noted that there is ongoing resistance to changing current guidelines. Much of this resistance, she argued, is based less on science than on the financial, personal and professional stakes many decision-makers have in maintaining the status quo.

She explained that various groups — including pharmaceutical and biotechnology companies, health systems, professional organizations that develop medical guidelines, and even patient advocacy groups — benefit directly or indirectly from the current definition of chronic kidney disease.

The forces driving over­diagnosis can be subtle and not always financial, O’Hare said. Some groups believe, for instance, that everything possible should be done to avoid kidney failure down the road, no matter how unlikely it might be.

Too often, Ravani said, doctors give credit for the patient’s survival to medication, when in fact it really made no difference.

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