New definition of chronic kidney disease labels one in eight adults as sick

A new definition of chronic kidney disease labels over 1 in 8 adults and around half of people over 70 years of age as having the disease. Yet low rates of kidney failure suggest many of those diagnosed will never progress to severe disease.

In BMJ today, Ray Moynihan and colleagues argue this is evidence of overdiagnosis. They call for a re-examination of the definition and urge clinicians to be cautious about labelling patients, particularly older people.

This article is the second of a series looking at the risks and harms of overdiagnosis in a range of common conditions. The series, together with the Preventing Overdiagnosis conference in September, are part of the BMJ's Too Much Medicine campaign to help tackle the threat to health and the waste of money caused by unnecessary care.

In 2002, a new framework for defining and classifying "chronic kidney disease" (CKD) was introduced. It defines chronic kidney disease as the presence of kidney damage or decreased kidney function for three months or more, irrespective of the cause, and is based largely on laboratory measures.

The framework has been widely embraced by many countries because it was assumed that earlier detection and treatment would slow progression towards kidney failure, and was updated in 2012.

But some doctors have raised concerns because the adoption of this definition has resulted in more than 1 in 8 adults (almost 14%) in the US being labelled as having chronic kidney disease and as many as 1 in 6 adults in Australia. Before the 2002 framework, it was estimated that 4.2 million Americans (1.7%) had chronic kidney disease.

In the UK, specialist referrals for chronic kidney disease are up 60% within a single NHS trust covering a population of 560,000 people, according to a University of Cardiff study, and up 40% at a hospital in Brisbane, Australia.

Advocates of the definition claim that "early detection can help prevent the progression of kidney disease." But despite the large numbers now labelled as having chronic kidney disease, low rates of kidney failure suggest many of those diagnosed will never progress to serious disease.

This say the authors, is evidence of overdiagnosis, and they point to the psychological effect of a disease label and the burden and costs of repeated assessment, testing, and potentially unnecessary treatment.

They argue that the benefits, harms, and costs of testing, monitoring, and treating the increased number of people being identified as having chronic kidney disease "need to be established by prospective studies."

They acknowledge that inferring overdiagnosis has limitations, but say the risk of overdiagnosis "warrants greater professional scrutiny and more public awareness" and they urge clinicians to be cautious about labelling patients, particularly older people.

"It is in everyone's interest to find the best way to maximise prevention of kidney disease and its consequences while minimising the risks and costs of overdiagnosis," they conclude.