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Ethnicity adjustment for kidney function testing removed from NICE chronic kidney disease guideline

25 August 2021

The National Institute of Health and Care Excellence (NICE) chronic kidney disease (CKD) guideline update, released today, has removed the recommendation to adjust for Black ethnicity when estimating how well a patient’s kidneys are working; a change that will prevent overestimation of kidney function in people from Black ethnic groups and enable early treatment for chronic kidney disease (CKD). 

How is kidney function estimated?

Estimated glomerular filtration rate (eGFR) is the most commonly used test to calculate how well a patient’s kidneys are working and determine their stage of kidney disease. If a patient’s eGFR is low, their kidneys are not working as well as they should be. 

eGFR is calculated using a specific equation based on the levels of creatinine - a waste product of muscle metabolism - in the patient’s blood. Damaged kidneys are less able to remove creatinine, so a high level can suggest reduced kidney function.  

People with more muscle mass (e.g. athletes) have higher creatinine production rates, and those with a lower muscle mass (e.g. people with a severe illness) have lower rates. Higher creatinine production rates than expected lead to falsely low eGFR, and lower creatinine production rates to falsely high eGFR. 

On average, the body’s production of creatinine falls with age and is lower in women than men, so the calculation is adjusted for age and sex.   

Adjustment for ethnicity

Until now, NICE and other authorities recommended that the calculated eGFR in a person from a Black ethnic group should be multiplied up by a “correction factor” of 1.159. This came as a result of studies from the US, which showed that people who self-identified as African-American generally had higher creatinine production rates, causing their eGFR to be falsely low. Many researchers assumed that this was because muscle mass was higher in African Americans, and that this difference was genetically determined. These findings led to the use of a ‘correction factor’ in people of Black ethnic backgrounds. There is no ethnicity adjustment for patients from any other ethnic groups and no provision for people of mixed ethnic origin. 

There have been no studies in the UK showing that individuals of Black ethnicity have higher creatinine production rates and our staff and researchers have been increasingly concerned that the adjustment for ethnicity doesn’t reflect the wide diversity within ethnic groups. For some patients, unnecessary adjustments could lead to overestimation of their eGFR, delayed diagnosis of chronic kidney disease, and a delay in treatment or transplant listing.  

The use of the correction factor has been a topic of concern for our Health Inequalities Working Group for some time in response to proposed changes in individual kidney units in the UK and the USA. Since March 2021, our trustee Dr Charlie Tomson has represented the charity as part of a working group organised by the Renal Association (now the UK Kidney Association) to push for a change in the NICE guideline.  

Removing ethnicity from the equation

In the 2021 NICE CKD guideline, the recommendation to adjust for ethnicity has been removed as it is no longer seen as valid or accurate. 

In the UK, people of Black ethnicity with CKD are at higher risk of kidney failure. We hope that by removing the possibility of overestimating kidney function in people of Black ethnicity, this will go some way towards dismantling the inequalities in healthcare faced by many people in the UK. 

Going forward, we urgently need better ways for doctors to estimate patients’ muscle mass if they are going to continue to use creatinine as the basis for estimating kidney function. Alternatively, we need to find ways of estimating kidney function that are not dependent on muscle mass. 

Any future research into improving the accuracy of eGFR calculations must ensure that all ethnic minority groups are fully represented. 

Dr Tomson said “This correction factor has never been validated in people of Black or African ethnicity in the UK, and it has become increasingly clear that its use is inappropriate, as it involves unjustifiable assumptions about the relationship between Black ethnicity and muscle mass. We desperately need more research both into how better to estimate kidney function in people of all ethnicities in the UK, and into the potential impact of the changes proposed by NICE on the numbers of people classified as having CKD.” 

Dr Aisling McMahon, executive director of research, innovation and policy at Kidney Research UK, said, “Eliminating health inequalities has long been one of our top priorities. We welcome and support the changes to the NICE CKD guidelines – these changes will ensure everyone is treated equally regardless of ethnicity.” 

Find out more

Take a look at the updated NICE chronic kidney disease guideline for more information.

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